the polymers of the invention generally include hydrophilic anion exchange resins , particularly aliphatic amine polymers . the “ amine ” group can be present in the form of a primary , secondary or tertiary amine , quaternary ammonium salt , amidine , guanadine , hydrazine , or combinations thereof . the amine can be within the linear structure of the polymer ( such as in polyethylenimine or a condensation polymer of a polyaminoalkane , e . g . diethylenetriamine , and a crosslinking agent , such as epichlorohydrin ) or as a functional group pendant from the polymer backbone ( such as in polyallylamine , polyvinylamine or poly ( aminoethyl ) acrylate ). in one aspect , the polymer is characterized by a repeating unit having the formula or a copolymer thereof , wherein n is an integer and each r , independently , is h or a substituted or unsubstituted alkyl , such as a lower alkyl ( e . g ., having between 1 and 5 carbon atoms , inclusive ), alkylamino ( e . g ., having between 1 and 5 carbons atoms , inclusive , such as ethylamino ) or aryl ( e . g ., phenyl ) group . in a second aspect , the polymer is characterized by a repeating unit having the formula or a copolymer thereof , wherein n is an integer , each r , independently , is h or a substituted or unsubstituted alkyl ( e . g ., having between 1 and 5 carbon atoms , inclusive ), alkylamino ( e . g ., having between 1 and 5 carbons atoms , inclusive , such as ethylamino ) or aryl ( e . g ., phenyl ) group , and each x − is an exchangeable negatively charged counterion . one example of a copolymer according to the second aspect of the invention is characterized by a first repeating unit having the formula wherein n is an integer , each r , independently , is h or a substituted or unsubstituted alkyl ( e . g ., having between 1 and 5 carbon atoms , inclusive ), alkylamino ( e . g ., having between 1 and 5 carbons atoms , inclusive , such as ethylamino ) or aryl group ( e . g ., phenyl ), and each x − is an exchangeable negatively charged counterion ; and further characterized by a second repeating unit having the formula wherein each n , independently , is an integer and each r , independently , is 11 or a substituted or unsubstituted alkyl ( e g ., having between 1 and 5 carbon atoms , inclusive ), alkylamino ( e . g ., having between 1 and 5 carbons atoms , inclusive , such as ethylamino ) or aryl group ( e . g ., phenyl ). in a fourth aspect , the polymer is characterized by a repeating unit having the formula or a copolymer thereof , wherein n is an integer , and r is h or a substituted or unsubstituted alkyl ( e . g ., having between 1 and 5 carbon atoms , inclusive ), alkylamino ( e . g ., having between 1 and 5 carbons atoms , inclusive , such as ethylamino ) or aryl group ( e . g ., phenyl ). one example of a copolymer according to the second aspect of the invention is characterized by a first repeating unit having the formula wherein n is an integer , and r is h or a substituted or unsubstituted alkyl ( e . g ., having between 1 and 5 carbon atoms , inclusive ), alkylamino ( e . g ., having between 1 and 5 carbons atoms , inclusive , such as ethylamino ) or aryl group ( e . g ., phenyl ); and further characterized by a second repeating unit having the formula wherein each n , independently , is an integer and r is h or a substituted or unsubstituted alkyl ( e . g ., having between 1 and 5 carbon atoms , inclusive ), alkylamino ( e . g ., having between 1 and 5 carbon atoms , inclusive , such as ethylamino ) or aryl group ( e . g ., phenyl ). in a fifth aspect , the polymer is characterized by a repeating group having the formula or a copolymer thereof , wherein n is an integer , and each r 1 and r 2 , independently , is h or a substituted or unsubstituted alkyl ( e . g ., having between 1 and 5 carbon atoms , inclusive ), and alkylamino ( e . g ., having between 1 and 5 carbons atoms , inclusive , such as ethylamino ) or aryl group ( e . g ., phenyl ), and each x − is an exchangeable negatively charged counterion . in one preferred polymer according to the fifth aspect of the invention , at least one of the r groups is a hydrogen atom . in a sixth aspect , the polymer is characterized by a repeat unit having the formula or a copolymer thereof , where n is an integer , each r 1 and r 2 , independently , is h , a substituted or unsubstituted alkyl group containing 1 to 20 carbon atoms , an alkylamino group ( e . g ., having between 1 and 5 carbons atoms , inclusive , such as ethylamino ), or an aryl group containing 6 to 12 atoms ( e . g ., phenyl ). in a seventh aspect , the polymer is characterized by a repeat unit having the formula or a copolymer thereof , wherein n is an integer , each r 1 , r 2 and r 3 , independently , is h , a substituted or unsubstituted alkyl group containing 1 to 20 carbon atoms , an alkylamino group ( e . g ., having between 1 and 5 carbons atoms , inclusive , such as ethylamino ), or an aryl group containing 6 to 12 atoms ( e . g ., phenyl ), and each x − is an exchangeable negatively charged counterion . in each case , the r groups can carry one or more substituents , suitable substituents include therapeutic anionic groups , e . g ., quaternary ammonium groups , or amine groups , e . g ., primary and secondary alkyl or aryl amines . examples of other suitable substituents include hydroxy , alkoxy , carboxamide , sulfonamide , halogen , alkyl , aryl , hydrazine , guanadine , urea , and carboxylic acid esters , for example . the polymers are preferably crosslinked , in some cases by adding a crosslinking agent to the reaction mixture during or after polymerization . examples of suitable crosslinking agents are diacrylates and dimethacrylates ( e . g ., ethylene glycol diacrylate , propylene glycol diacrylate , butylene glycol diacrylate , ethylene glycol dimethacrylate , propylene glycol dimethacrylate , butylene glycol dimethacrylate , polyethyleneglycol dimethacrylate , polyethyleneglycol diacrylate ), methylene bisacrylamide , methylene bismethacrylamide , ethylene bisacrylamide , epichlorohydrin , epibromohydrin , toluene diisocyanate , ethylenebismethacrylamide , ethylidene bisacrylamide , divinyl benzene , bisphenol a dimethacrylate , bisphenol a diacrylate , 1 , 4 butanedioldiglycidyl ether , 1 , 2 ethanedioldiglycidyl ether , 1 , 3 - dichloropropane , 1 , 2 - dichloroethane , 1 , 3 - dibromopropane , 1 , 2 - dibromoethane , succinyl dichloride , dimethylsuccinate , acryloyl chloride , or pyromellitic dianhydride . the amount of crosslinking agent is typically between about 0 . 5 and about 75 weight %, and preferably between about 1 and about 25 % by weight , based upon the combined weight of crosslinking and monomer . in another embodiment , the crosslinking agent is present between about 2 and about 20 % by weight of polymer . in some cases the polymers are crosslinked after polymerization . one method of obtaining such crosslinking involves reaction of the polymer with difunctional crosslinkers , such as epichlorohydrin , succinyl dichloride , the diglycidyl ether of bisphenol a , pyromellitic dianhydride , toluence diisocyanate , and ethylenediamine . a typical example is the reaction of poly ( ethyleneimine ) with epichlorohydrin . in this example the epichlorohydrin ( 1 to 100 parts ) is added to a solution containing polyethyleneimine ( 100 parts ) and heated to promote reaction . other methods of inducing crosslinking on already polymerized materials include , but are not limited to , exposure to ionizing radiation , ultraviolet radiation , electron beams , radicals , and pyrolysis . examples of preferred crosslinking agents include epichlorohydrin , 1 , 4 butanedioldiglycidyl ether , 1 , 2 ethanedioldiglycidyl ether , 1 , 3 - dichloropropane , 1 , 2 - dichloroethane , 1 , 3 - dibromopropane , 1 , 2 - dibromoethane , succinyl dichloride , dimethylsuccinate , toluene diisocyanate , acryloyl chloride , and pyromellitic dianhydride . the negatively charged counterions , x − , can be organic ions , inorganic ions , or a combination thereof . the inorganic ions suitable for use in this invention include halide ( especially chloride ), carbonate , bicarbonate , sulfate , bisulfate , hydroxide , nitrate , persulfate and sulfite . suitable organic ions include acetate , ascorbate , benzoate , citrate , dihydrogen citrate , hydrogen citrate , oxalate , succinate , tartrate , taurocholate , glycocholate , and cholate . in a preferred embodiment , the counterion does not have a detrimental side effect to the patient but rather is selected to have a therapeutic or nutritional benefit to the patient . candidate polymers were tested by stirring them in a phosphate containing solution at ph 7 for 3 hours . the solution was designed to mimic the conditions present in the small intestine . the ph was adjusted to ph 7 , once at the start of the test and again at the end of the test , using either aqueous naoh or hcl . after 3 hours the polymer was filtered off and the residual phosphate concentration in the test solution was determined spectrophotometrically . the difference between the initial phosphate concentration and the final concentration was used to determine the amount of phosphate bound to the polymer . this result is expressed in milliequivalents per gram of starting polymer ( meq / g ). table 1 below shows the results obtained for several polymers . higher numbers indicate a more effective polymer . oxabsorb ® is an organic polymer that encapsulates calcium such that the calcium is available to bind to such ions as phosphate , but may not be released by the polymer and thus is not supposed to be absorbed by the patient . the amount of phosphate bound by all of these materials , both polymers and inorganic gels , is expected to vary as the phosphate concentration varies . the graph fig1 below shows the relationship between the solution phosphate concentration and the amount of phosphate bound to poly ( dimethylaminopropylacrylamide ). other polymers of the class are expected to show a similar relationship . in an alternate type of test , the polymer was exposed to an acidic environment prior to exposure to phosphate as might happen in a patient &# 39 ; s stomach . the solid ( 0 . 1 g ) was suspended in 40 ml of 0 . 1 m nacl . this mixture was stirred for 10 minutes , and the ph was adjusted to 3 . 0 with 1 m hcl , and the mixture was stirred for 30 minutes . the mixture was centrifuged , the supernatant decanted , and the solid resuspended in 40 ml of 0 . 1 m nacl . this mixture was stirred for 10 minutes , the ph was adjusted to 3 . 0 with 1 m hcl , and the mixture was stirred for 30 minutes . the mixture was centrifuged , the supernatant decanted , and the solid residue used in the usual phosphate assay . results are shown in table 4 for a variety of polymers and for aluminum hydroxide dried gel . in most cases the values for the amount of phosphate bound are higher in this test than in the usual assay . six 6 - 8 week old sprague - dawley rats were placed in metabolic cages and fed semi - purified rodent chow powder containing 0 . 28 % inorganic phosphorus . the diets were supplemented with 1 . 7 % poly ( allylamine / epichlorohydrin ) or micro - crystalline cellulose ; the animals served as their own controls by receiving cellulose or poly ( allylamine / epichlorohydrin ) in randomized order . the rats were fed ad libitum for three days to acclimate to the diet . feces excreted during the next 48 hours were collected , lyophilized , and ground into powder . the inorganic phosphate content was determined according to the method of taussky and shorr : microdetermination of inorganic phosphate . one gram of powdered feces was burned to remove carbon , then ashed in a 600 ° c . oven . concentrated hcl was then added to dissolve the phosphorus . the phosphorus was determined with ferrous sulfate - ammonium molybdate reagent . intensity of the blue color was determined at 700 nm on a perkin - elmer spectrophotometer through a 1 cm cell . the results are shown in fig2 . fecal phosphate concentration increased in all animals . one kidney was surgically removed ; approximately 50 % of the renal artery flow to the contralateral kidney was ligated . the animals were fed a semi - purified rodent chow containing 0 . 385 % inorganic phosphorus and either 10 % poly ( allylamine / epichlorohydrin ) or cellulose . urine was collected and analyzed for phosphate content on specific days . absorbed dietary phosphate is excreted into the urine to maintain serum phosphate . the results are shown in fig3 . none of the animals became hyperphosphatemic or uremic , indicating that the residual kidney function was adequate to filter the absorbed phosphate load . the animals receiving the poly ( allylamine / epichlorohydrin ) demonstrated a trend towards reduced phosphate excretion , indicative of reduced phosphate absorption . poly ( allylamine hydrochloride )— to a 5 l , water jacketed reaction kettle equipped with 1 ) a condenser topped with a nitrogen gas inlet and 2 ) a thermometer and 3 ) a mechanical stirrer was added concentrated hydrochloric acid ( 2590 ml ). the acid was cooled to 5 ° c . using circulating water in the jacket of the reaction kettle at 0 ° c . allylamine ( 2362 ml ; 1798 g ) was added dropwise with stirring , maintaining a temperature of 5 - 10c . after the addition was complete , 1338 ml of liquid was removed by vacuum distillation at 60 - 70 ° c . azobis ( amidinopropane ) dihydrochloride ( 36 g ) suspended in 81 ml water was added . the kettle was heated to 50 ° c . under a nitrogen atmosphere with stirring for 24 hours . azobis ( amidinopropane ) dihydrochloride ( 36 g ) suspended in 81 ml water was again added and the heating and stirring continued for an additional 44 hours . distilled water ( 720 ml ) was added and the solution allowed to cool with stirring . the liquid was added dropwise to a stirring solution of methanol ( 30 l ). the solid was then removed by filtration , resuspended in methanol ( 30 l ), stirred 1 hour , and collected by filtration . this methanol rinse was repeated once more and the solid was dried in a vacuum oven to yield 2691 g of a granular white solid ( poly ( allylamine hydrochloride ). poly ( allylamine / epichlorohydrin )— to a 5 gallon bucket was added poly ( allylamine hydrochloride ) ( 2 . 5 kg ) and water 10 l ). the mixture was stirred to dissolve and the ph was adjusted to 10 with a solid naoh . the solution was allowed to cool to room temperature in the bucket and epichlorohydrin ( 250 ml ) was added all at once with stirring . the mixture was stirred gently until it gelled after about 15 minutes . the gel was allowed to continue curing for 18 hours at room temperature . the gel was then removed and put into a blender with isopropanol ( about 7 . 5 l ). the gel was mixed in the blender with about 500 ml isopropanol for ˜ 3 minutes to form coarse particles and the solid was then collected by filtration . the solid was rinsed three times by suspending it in 9 gallons of water , stirring the mixture for 1 hour , and collecting the solid by filtration . the solid was rinsed once by suspending it in isopropanol ( 60 l ), stirring the mixture for 1 hour , and collecting the solid by filtration . the solid was dried in a vacuum oven for 18 hours to yield 1 . 55 kg of a granular , brittle , white solid . poly ( allylamine / butanedioldiglycidyl ether )— to a 5 gallon plastic bucket was added poly ( allylamine hydrochloride ) ( 500 g ) and water ( 2 l ). the mixture was stirred to dissolve and the ph was adjusted to 10 with solid naoh ( 142 . 3 g ). the solution was allowed to cool to room temperature in the bucket and 1 , 4 - butanedioldiglycidyl ether ( 130 ml ) was added all at once with stirring . the mixture was stirred gently until it gelled after 4 minutes . the gel was allowed to continue curing for 18 hours at room temperature . the gel was then removed and dried in a vacuum oven at 75 ° c . for 24 hours . the dry solid was ground and sieved for − 30 mesh and then suspended in 6 gallons on water . after stirring for 1 hour the solid was filtered off and rinse process repeated twice more . the solid was rinsed twice in isopropanol ( 3 gallons ), and dried in a vacuum oven at 50 ° c . for 24 hours to yield 580 g of a white solid . poly ( allylamine / ethanedioldiglycidyl ether )— to a 100 ml beaker was added poly ( allylamine hydrochloride ) ( 10 g ) and water ( 40 ml ). the mixture was stirred to dissolve and the ph was adjusted to 10 with solid naoh . the solution was allowed to cool to room temperature in the beaker and 1 , 2 ethanedioldiglycidyl ether ( 2 . 0 ml ) was added all at once with stirring . the mixture was allowed to continue curing for 18 hours at room temperature . the gel was then removed and blended in 500 ml of methanol . the solid was filtered off and suspended in water ( 500 ml ). after stirring for 1 hour the solid was filtered off and the rising process repeated . the solid was rinsed twice in isopropanol ( 400 ml ), and dried in a vacuum oven at 50 ° c . for 24 hours to yield 8 . 7 g of a white solid . poly ( allylamine / dimethylsuccinate )— to a 500 ml round bottom flask was added poly ( allylamine hydrochloride ) ( 10 g ), methanol ( 100 ml ), and triethylamine ( 10 ml ). the mixture was stirred and dimethylsuccinate ( 1 ml ) was added . the solution was heated to reflux and stirring turned off after 30 minutes . after 18 hours the solution was cooled to room temperature and solid was filtered off and suspended in water ( 1 l ). after stirring for 1 hour the solid was filtered off and the rinse process repeated twice more . the solid was rinsed once in isopropanol ( 800 ml ), and dried in a vacuum oven at 50 ° c . for 24 hours to yield 5 . 9 g of a white solid . poly ( allyltrimethylammonium chloride )— to a 500 ml three necked flask equipped with a magnetic stirrer , a thermometer , and a condenser topped with a nitrogen inlet , was added poly ( allylamine ) crosslinked with epichlorohydrin ( 5 . 0 g ), methanol ( 300 ml ), methyl iodide ( 20 ml ), and sodium carbonate ( 50 g ). the mixture was then cooled and water was added to total volume of 2 l . concentrated hydrochloric acid was added until no further bubbling resulted and the remaining solid was filtered off . the solid was rinsed twice in 10 % aqueous nacl ( 1 l ) by stirring for 1 hour followed by filtration to recover the solid . the solid was then rinsed three times by suspending it in water ( 2 l ), stirring for 1 hour , and filtering to recover the solid . finally , the solid was rinsed as above in methanol and dried in a vacuum over at 50 ° c . for 18 hours to yield 7 . 7 g of white granular solid . poly ( ethyleneimine )/ acryloyl chloride — into a 5 l three neck flask equipped with a mechanical stirrer , a thermometer , and an additional funnel was added polyethyleneimine ( 510 g of a 50 % aqueous solution ( equivalent to 255 g of dry polymer ) and isopropanol ( 2 . 5 l ). acryloyl chloride ( 50 g ) was added dropwise through the addition funnel over a 35 minute period , keeping the temperature below 29 ° c . the solution was then heated to 60 ° c . with stirring for 18 hours . the solution was cooled and solid immediately filtered off . the solid was rinsed three times by suspending it in water ( 2 gallons ), stirring for 1 hour , and filtering to recover the solid . the solid was rinsed once by suspending it in methanol ( 2 gallons ), stirring for 30 minutes , and filtering to recover the solid . finally , the solid was rinsed as above in isopropanol and dried in a vacuum over at 50 ° c . for 18 hours to yield 206 g of light orange granular solid . poly ( dimethylaminopropylacrylamide )— dimethylamino - propylacrylamide ( 10 g ) and methylene - bisacrylamide ( 1 . 1 g ) were dissolved in 50 ml of water in a 100 ml three neck flask . the solution was stirred under nitrogen for 10 minutes . potassium persulfate ( 0 . 3 g ) and sodium metabisulfite ( 0 . 3 g ) were each dissolved in 2 - 3 ml of water and then mixed . after a few seconds this solution was added to the monomer solution , still under nitrogen . a gel formed immediately and was allowed to sit overnight . the gel was removed and blended with 500 ml of isopropanol . the solid was filtered off and rinsed three times with acetone . the solid white powder was filtered off and dried in a vacuum oven to yield 6 . 1 g . poly ( methacrylamidopropyltrimethylammoniumchloride )=[ poly ( maptac )]-[ 3 -( methacryloylamino ) propyl ] trimethylammonium chloride ( 38 ml of 50 % aqueous solution ) and methylenebis - methacrylamide ( 2 . 2 g ) were stirred in a beaker at room temperature . methanol ( 10 ml was added and the solution was warmed to 40 ° c . to fully dissolve the bisacrylamide . potassium persulfate ( 0 . 4 g ) was added and the solution stirred for 2 minutes . potassium metabisulfite ( 0 . 4 g ) was added and stirring was continued . after 5 minutes the solution was put under a nitrogen atmosphere . after 20 minutes the solution contained significant precipitate and the solution was allowed to sit overnight . the solid was washed three times with isopropanol and collected by filtration . the solid was then suspended in water 500 ( ml ) and stirred for several hours before being collected by centrifugation . the solid was again washed with water and collected by filtration . the solid was then dried in a vacuum oven to yield 21 . 96 g . poly ( ethyleneimine ) “ a ”— polyethyleneimine ( 50 g of a 50 % aqueous solution ; scientific polymer products ) was dissolved in water ( 100 ml ). epichlorohydrin ( 4 . 6 ml ) was added dropwise . the solution was heated to 55 ° c . for 4 hours , after which it had gelled . the gel was removed , blended with water ( 1 l ) and the solid was filtered off . it was resuspended in water ( 2 l ) and stirred for 10 minutes . the solid was filtered off , the rinse repeated once with water and twice with isopropanol , and the resulting gel was dried in a vacuum oven to yield 26 . 3 g of a rubbery solid . poly ( ethyleneimine ) “ b ” and poly ( ethyleneimine ) “ c ” were made in a similar manner , except using 9 . 2 and 2 . 3 ml of epichlorohydrin , respectively . poly ( methylmethacrylate - co - divinylbenzene )— methylmeth - acrylate ( 50 g ) and divinylbenzene ( 5 g ) and azobisiso - butyronitrile ( 1 . 0 g ) were dissolved in isopropanol ( 500 ml ) and heated to reflux for 18 hours under a nitrogen 14 atmosphere . the solid white precipitate was filtered off , rinsed once in acetone ( collected by centrifugation ), once in water ( collected by filtration and dried in a vacuum oven to yield 19 . 4 g . poly ( diethylenetriaminemethacrylamide )— poly ( methyl - methacrylate - co - divinylbenzene ) ( 20 g ) was suspended in diethylenetriamine ( 200 ml ) and heated to reflux under a nitrogen atmosphere for 18 hours . the solid was collected by filtration , resuspended in water ( 500 ml ), stirred 30 minutes , filtered off , resuspended in water ( 500 ml ), stirred 30 minutes , filtered off , rinsed briefly in isopropanol , and dried in a vacuum oven to yield 18 . 0 g . poly ( pentaethylenehexaminemethacrylamide ), poly ( tetr - aethylenepentamine - methacrylamide ), and poly ( trie - thylenetetraaminemethacrylamide ) were made in a manner similar to poly ( diethylenetriaminemethacrylamide ) from pentaethylenehexamine , tetraethylenepentamine , and triethylenetetraamine , respectively . poly ( methylmethacrylate / pei )— poly ( methylmethacrylate - co - divinylbenzene ) ( 1 . 0 g ) was added to a mixture containing hexanol ( 9150 ml ) and polyethyleneimine ( 15 g in 15 g water ). the mixture was heated to reflux under nitrogen for 4 days . the reaction was cooled and the solid was filtered off , suspended in methanol ( 300 ml ), stirred 1 hour , and filtered off . the rinse was repeated once with isopropanol and the solid was dried in a vacuum oven to yield 0 . 71 g . poly ( aminoethylmethacrylamide )— poly ( methylmethacrylate - co - divinylbenzene ) ( 20 g ) was suspended in ethylenediamine 9200 ml ) and heated to reflux under a nitrogen atmosphere for 3 days . the solid was collected by centrifugation , washed by resuspending it in water ( 500 ml ), stirring for 30 minutes , and filtering off the solid . the solid was washed twice more in water , once in isopropanol , and dried in a vacuum oven to yield 17 . 3 g . poly ( dimethylaminopropylacrylamide )— poly ( methyl - methacrylate - co - divinylbenzene ) ( 20 g ) was suspended in diethylaminopropylamine ( 200 ml ) and heated to reflux under a nitrogen atmosphere for 18 hours . the solid was collected by filtration , resuspended in water ( 500 ml ), filtered off , resuspended in water ( 500 ml ), collected by filtration , rinsed briefly in isopropanol , and dried in a vacuum oven to yield 8 . 2 g . nhs - acrylate — n - hydroxysuccinimide ( nhs , 157 . 5 g ) was dissolved in chloroform ( 2300 ml ) in a 5 l flask . the solution was cooled to 0 ° c . and acryloyl chloride ( 132 g ) was added dropwise , keeping the temperature 2 ° c . after addition was complete , the solution was stirred for 1 . 5 hours , rinsed with water ( 1100 ml ) in a separatory funnel and dried over anhydrous sodium sulfate . the solvent was removed under vacuum and a small amount of ethyl acetate was added to the residue . this mixture was poured into hexane ( 200 ml ) with stirring . the solution was heated to reflux , adding more ethyl acetate ( 400 ml ). the insoluble nhs was filtered off , hexane ( 1 l ) was added , the solution was heated to reflux , ethyl acetate ( 400 ml ) was added , and the solution allowed to cool to & lt ; 10 ° c . the solid was then filtered off and dried in a vacuum oven to yield 125 . 9 g . a second crop of 80 g was subsequently collected by further cooling . poly ( nhs - acrylate )— nhs - acrylate ( 28 . 5 g ), methylenebis - acrylamide ( 1 . 5 g ) and tetrahydrofuran ( 500 ml ) were mixed in a 1 l flask and heated to 50 ° c . under a nitrogen atmosphere . azobisisobutyronitrile ( 0 . 2 g ) was added , the solution was stirred for 1 hour , filtered to remove excess n - hydroxysuccinimide , and heated to 50 ° c . for 4 . 5 hours under a nitrogen atmosphere . the solution was then cooled and the solid was filtered off , rinsed in tetrahydrofuran , and dried in a vacuum oven to yield 16 . 1 g . poly ( guanidinobutylacrylamide )— poly ( nhs - acrylate ) ( 1 . 5 g ) was suspended in water ( 25 ml ) containing agmatine ( 1 . 5 g ) which had been adjusted to ph 9 with solid naoh . the solution was stirred for 4 days , after which time the ph had dropped to 6 . 3 . water was added to a total of 500 ml , the solution was stirred for 30 minutes and the solid was filtered off . the solid was rinsed twice in water , twice in isopropanol , and dried in a vacuum oven to yield 0 . 45 g . poly ( methacryloyl chloride )— methacryloyl chloride ( 20 ml ), divinyl benzene ( 4 ml of 80 % purity ), aibn ( 0 . 4 g ), and thf ( 150 ml ) were stirred at 60 ° c . under a nitrogen atmosphere for 18 hours . the solution was cooled and the solid was filtered off , rinsed in thf , then acetone , and dried in a vacuum oven to yield 8 . 1 g . poly ( guanidinobutylmethacrylamide )— poly ( methacryloyl chloride ) ( 0 . 5 g ), agmatine sulfate ( 1 . 0 g ), triethylamine ( 2 . 5 ml ), and acetone ( 50 ml ) were stirred together for 4 days . water ( 100 ml ) was added and the mixture stirred for 6 hours . the solid was filtered off and washed by resuspending in water ( 500 ml ), stirring for 30 minutes , and filtering off the solid . the wash was repeated twice in water , once in methanol , and the solid was dried in a vacuum oven to yield 0 . 41 g . poly ( guanidinoacrylamide )— the procedure for poly -( guanidinobutylacrylamide ) was followed substituting aminoguanidine bicarbonate ( 5 . 0 g ) for the agmatine , yielding 0 . 75 g . poly ( peh / epi )— epichlorohydrin ( 1 . 5 g ) was added dropwise to a solution containing pentaethylenehexamine ( 20 g ) and water ( 100 ml ), keeping the temperature between 65 ° c . the solution was stirred until it gelled and heating was continued for 4 hours ( at 65 ° c .). after sitting overnight at room temperature the gel was removed and blended with water ( 1 l ). the solid was filtered off , water was added ( 1 l ), and the blending and filtration were repeated . the gel was suspended in isopropanol and the resulting solid was collected by filtration and dried in a vacuum oven to yield 28 . 2 g . ethylidenebisacetamide — acetamide ( 118 g ), acetaldehyde ( 44 . 06 g ), copper acetate ( 0 . 2 g ), and water ( 300 ml ) were placed in a 1 l three neck flask fitted with condenser , thermometer , and mechanical stirred . concentrated hcl ( 34 ml ) was added and the mixture was heated to 45 - 50 ° c . with stirring for 24 hours . the water was then removed in vacuo to leave a thick sludge which formed crystals on cooling to 5 ° c . acetone ( 200 ml ) was added and stirred for a few minutes after which the solid was filtered off and discarded . the acetone was cooled to 0 ° c . and solid was filtered off . this solid was rinsed in 500 ml acetone and air dried 18 hours to yield 31 . 5 g . vinylacetamide — ethylidenebisacetamide ( 31 . 05 ), calcium carbonate ( 2 g ) and celite 541 ( 2 g ) were placed in a 500 ml three neck flask fitted with a thermometer , a mechanical stirrer , and a distilling head atop a vigroux column . the mixture was vacuum distilled at 35 mm hg by heating the pot to 180 - 225 ° c . only a single fraction was collected ( 10 . 8 g ) which contained a large portion of acetamide in addition to the product ( determined by nmr ). this solid product was dissolved in isopropanol ( 30 ml ) to form the crude solution used for polymerization . poly ( vinylacetamide )— crude vinylacetamide solution ( 15 ml ), divinylbenzene ( 1 g , technical grade , 55 % pure , mixed isomers ), and aibn ( 0 . 3 g ) were mixed and heated to reflux under a nitrogen atmosphere for 90 minutes , forming a solid precipitate . the solution was cooled , isopropanol ( 50 ml ) was added , and the solid was collected by centrifugation . the solid was rinsed twice in isopropanol , once in water , and dried in a vacuum oven to yield 0 . 8 g . poly ( vinylamine )— poly ( vinylacetamide ) ( 0 . 79 g ) was placed in a 100 ml one neck flask containing water 25 ml and concentrated hcl 25 ml . the mixture was refluxed for 5 days , the solid was filtered off , rinsed once in water , twice in isopropanol , and dried in a vacuum oven to yield 0 . 77 g . the product of this reaction (˜ 0 . 84 g ) was suspended in naoh ( 46 g ) and water ( 46 g ) and heated to boiling (˜ 140 ° c .). due to foaming the temperature was reduced and maintained at ˜ 100 ° c . for 2 hours . water ( 100 ml ) was added and the solid collected by filtration . after rinsing once in water the solid was suspended in water ( 500 ml ) and adjusted to ph 5 with acetic acid . the solid was again filtered off , rinsed with water , then the isopropanol , and dried in a vacuum oven to yield 0 . 51 g . poly ( trimethylammoniomethylstyrene chloride ) is the copolymer of trimethylammoniomethylstyrene chloride and divinyl benzene . poly ( det / epi ) is the polymer formed by reaction of diethylenetriamine and epichlorohydrin . poly ( ethyleneimine ) salts — polyethyleneimine ( 25 g dissolved in 25 g water ) was dissolved in water ( 100 ml ) and mixed with toluene ( 1 l ). epichlorohydrin ( 2 . 3 ml ) was added and the mixture heated to 60 ° c . with vigorous mechanical stirring for 18 hours . the mixture was cooled and the solid filtered off , resuspended in methanol ( 2 l ), stirred 1 hour , and collected by centrifugation . the solid was suspended in water ( 2 l ), stirred 1 hour , filtered off , suspended in water ( 4 l ), stirred 1 hour , and again filtered off . the solid was suspended in acetone ( 4 l ) and stirred 15 minutes , the liquid was poured off , acetone ( 2 l ) was added , the mixture was stirred 15 minutes , the acetone was again poured off , and the solid was dried in a vacuum oven to form intermediate “ d ”. poly ( ethyleneimine sulfate a )— intermediate “ d ” ( 1 . 0 g ) was suspended in water ( 150 ml ), stirred 30 minutes , and partially neutralized with sulfuric acid ( 1 . 1 g ). the mixture was stirred an additional 30 minutes , the solid was filtered off , resuspended in methanol ( 200 ml ), stirred 5 minutes , filtered off , and dried in a vacuum oven . poly ( ethyleneimine sulfate b )— intermediate “ d ” ( 1 . 0 g ) was suspended in water ( 150 ml ), stirred 30 minutes , and partially neutralized with sulfuric acid ( 0 . 57 g ). the mixture was stirred an additional 30 minutes , the solid was filtered off , resuspended in methanol ( 200 ml ), stirred 5 minutes , filtered off , and dried in a vacuum oven . poly ( ethyleneimine sulfate c )— intermediate “ d ” ( 1 . 0 g ) was suspended in water ( 150 ml ), stirred 30 minutes , and partially neutralized with sulfuric acid ( 0 . 28 g ). the mixture was stirred an additional 30 minutes , the solid was filtered off , resuspended in methanol ( 200 ml ), stirred 5 minutes , filtered off , and dried in a vacuum oven . poly ( ethyleneimine sulfate d )— intermediate “ d ” ( 1 . 0 g ) was suspended in water ( 150 ml ), stirred 30 minutes , and partially neutralized with sulfuric acid ( 0 . 71 g ). the mixture was stirred an additional 30 minutes , the solid was filtered off , resuspended in methanol ( 200 ml ), stirred 5 minutes , filtered off , and dried in a vacuum oven . poly ( ethyleneimine tartrate a )— intermediate “ d ” ( 1 . 0 g ) was suspended in water ( 150 ml ), stirred 30 minutes , and partially neutralized with tartaric acid ( 1 . 72 g ). the mixture was stirred an additional 30 minutes , the solid was filtered off , resuspended in methanol ( 200 ml ), stirred 5 minutes , filtered off , and dried in a vacuum oven . poly ( ethyleneimine tartrate b )— intermediate “ d ” ( 1 . 0 g ) was suspended in water ( 150 ml ), stirred 30 minutes , and partially neutralized with tartaric acid ( 0 . 86 g ). the mixture was stirred an additional 30 minutes , the solid was filtered off , resuspended in methanol ( 200 ml ), stirred 5 minutes , filtered off , and dried in a vacuum oven . poly ( ethyleneimine tartrate c )— intermediate “ d ” ( 1 . 0 g ) was suspended in water ( 150 ml ), stirred 30 minutes , and partially neutralized with tartaric acid ( 0 . 43 g ). the mixture was stirred an additional 30 minutes , the solid was filtered off , resuspended in methanol ( 200 ml ), stirred 5 minutes , filtered off , and dried in a vacuum oven . poly ( ethyleneimine ascorbate a )— intermediate “ d ” ( 1 . 0 g ) was suspended in water ( 150 ml ), stirred 30 minutes , and partially neutralized with ascorbic acid ( 4 . 05 g ). the mixture was stirred an additional 30 minutes , the solid was filtered off , resuspended in methanol ( 200 ml ), stirred 5 minutes , filtered off , and dried in a vacuum oven . poly ( ethyleneimine ascorbate b )— intermediate “ d ” ( 1 . 0 g ) was suspended in water ( 150 ml ), stirred 30 minutes , and partially neutralized with ascorbic acid ( 2 . 02 g ). the mixture was stirred an additional 30 minutes , the solid was filtered off , resuspended in methanol ( 200 ml ), stirred 5 minutes , filtered off , and dried in a vacuum oven . poly ( ethyleneimine ascorbate c )— intermediate “ d ” ( 1 . 0 g ) was suspended in water ( 150 ml ), stirred 30 minutes , and partially neutralized with ascorbic acid ( 1 . 01 g ). the mixture was stirred an additional 30 minutes , the solid was filtered off , resuspended in methanol ( 200 ml ), stirred 5 minutes , filtered off , and dried in a vacuum oven . poly ( ethyleneimine citrate a )— intermediate “ d ” ( 1 . 0 g ) was suspended in water ( 150 ml ), stirred 30 minutes , and partially neutralized with citric acid ( 1 . 47 g ). the mixture was stirred an additional 30 minutes , the solid was filtered off , resuspended in methanol ( 200 ml ), stirred 5 minutes , filtered off , and dried in a vacuum oven . poly ( ethyleneimine citrate b )— intermediate “ d ” ( 1 . 0 g ) was suspended in water ( 150 ml ), stirred 30 minutes , and partially neutralized with citric acid ( 0 . 74 g ). the mixture was stirred an additional 30 minutes , the solid was filtered off , resuspended in methanol ( 200 ml ), stirred 5 minutes , filtered off , and dried in a vacuum oven . poly ( ethyleneimine citrate c )— intermediate “ d ” ( 1 . 0 g ) was suspended in water ( 150 ml ), stirred 30 minutes , and partially neutralized with citric acid ( 0 . 37 g ). the mixture was stirred an additional 30 minutes , the solid was filtered off , resuspended in methanol ( 200 ml ), stirred 5 minutes , filtered off , and dried in a vacuum oven . poly ( ethyleneimine succinate a )— intermediate “ d ” ( 1 . 0 g ) was suspended in water ( 150 ml ), stirred 30 minutes , and partially neutralized with succinic acid ( 1 . 36 g ). the mixture was stirred an additional 30 minutes , the solid was filtered off , resuspended in methanol ( 200 ml ), stirred 5 minutes , filtered off , and dried in a vacuum oven . poly ( ethyleneimine succinate b )— intermediate “ d ” ( 1 . 0 g ) was suspended in water ( 150 ml ), stirred 30 minutes , and partially neutralized with succinic acid ( 0 . 68 g ). the mixture was stirred an additional 30 minutes , the solid was filtered off , resuspended in methanol ( 200 ml ), stirred 5 minutes , filtered off , and dried in a vacuum oven . poly ( ethyleneimine chloride )— polyethyleneimine ( 100 g in 100 g water ) was dissolved in water ( 640 ml additional ) and the ph was adjusted to 10 with concentrated hcl . isopropanol ( 1 . 6 l ) was added , followed by epichlorohydrin ( 19 . 2 ml ). the mixture was stirred under nitrogen for 18 hours at 60 ° c . the solids were filtered off and rinsed with methanol ( 300 ml ) on the funnel . the solid was rinsed by resuspending it in methanol ( 4 l ), stirring 30 minutes , and filtering off the solid . the rinse was repeated twice with methanol , followed by resuspension in water ( 1 gallon ). the ph was adjusted to 1 . 0 with concentrated hcl , the solid was filtered off , resuspended in water ( 1 gallon ), the ph again adjusted to 1 . 0 with concentrated hcl , the mixture stirred 30 minutes , and the solid filtered off . the methanol rinse was again repeated and the solid dried in a vacuum oven to yield 112 . 4 g . poly ( dimethylethyleneimine chloride )— poly ( ethyleneimine chloride ) ( 5 . 0 g ) was suspended in methanol ( 300 ml ) and sodium carbonate ( 50 g ) was added . methyl iodide ( 20 ml ) was added and the mixture heated to reflux for 3 days . water was added to reach a total volume of 500 ml , the mixture stirred for 15 minutes , and the solid filtered off . the solid was suspended in water ( 500 ml ), stirred 30 minutes , and filtered . the solid was suspended in water ( 1 l ), the ph adjusted to 7 . 0 with concentrated hcl , and the mixture stirred for 10 minutes . the solid was filtered off , resuspended in isopropanol ( 1 l ), stirred 30 minutes , filtered off , and dried in a vacuum oven to yield 6 . 33 g . the methods of the invention involve treatment of patients with hyperphosphatemia . elevated serum phosphate is commonly present in patients with renal insufficiency , hypoparathyroidism , pseudohypoparathyroidism , acute untreated acromegaly , overmedication with phosphate salts , and acute tissue destruction as occurs during rhabdomyolysis and treatment of malignancies . the term “ patient ” used herein is taken to mean any mammalian patient to which phosphate binders may be administered . patients specifically intended for treatment with the methods of the invention include humans , as well as nonhuman primates , sheep , horses , cattle , goats , pigs , dogs , cats , rabbits , guinea pigs , hamsters , gerbils , rats and mice . the compositions utilized in the methods of the inventions are orally administered in therapeutically effective amounts . further , the polymer are preferably non - toxic and stable upon administration . a therapeutically effective amount of compound is that amount which produces a result or exerts an influence on the particular condition being treated . as used herein , a therapeutically effective amount of a phosphate binder means an amount which is effective in decreasing the serum phosphate levels of the patient to which it is administered . by “ non - toxic ” it is meant that when ingested in therapeutically effective amounts neither the polymers nor any ions released into the body upon ion exchange are harmful or are substantially harmful . by “ stable ” it is meant that when ingested in therapeutically effective amounts the polymers do not dissolve or otherwise decompose to form potentially harmful by - products , and remain substantially intact so that they can transport bound phosphate out of the body . the present pharmaceutical compositions are generally prepared by known procedures using well known and readily available ingredients . in making the compositions of the present invention , the polymeric phosphate binder may be present alone , may be admixed with a carrier , diluted by a carrier , or enclosed within a carrier which may be in the form of a capsule , sachet , paper or other container . when the carrier serves as a diluent , it may be a solid , semi - solid or liquid material which acts as a vehicle , excipient or medium for the polymer . thus , the compositions can be in the form of tablets , pills , powders , lozenges , sachets , cachets , elixirs , suspensions , syrups , aerosols , ( as a solid or in a liquid medium ), soft or hard gelatin capsules , sterile packaged powders , and the like . examples of suitable carrier , excipients , and diluents include foods , drinks , lactose , dextrose , sucrose , sorbitol , mannitol , starches , gum acacia , alginates , tragacanth , gelatin , calcium silicate , microcrystalline cellulose , polyvinylpyrrolidone , cellulose , methyl cellulose , methylhydroxybenzoates , propylhydroxybenzoates , propylhydroxybenzoates , and talc . it should be understood , however , that the foregoing description of the invention is intended merely to be illustrative by way of example only and than other modifications , embodiments , and equivalents may be apparent to those skilled in the art without departing from its spirit .
phosphate - binding polymers are provided for removing phosphate from the gastrointestinal tract . the polymers are orally administered , and are useful for the treatment of hyperphosphatemia .