Study On Functionalization Of Biodegradable Polymers

Biodegradable polymeric materials are the polymeric materials which can be degraded by bacteria,fungi,mildew,algae and their secretions under enzyme action or chemical decomposition.According to the source,biodegradable polymeric materials can be classified into two categories:synthetic biodegradable polymeric materials and natural biodegradable polymeric materials.However,the unmodified biodegradable polymeric materials are hard to mould since the poor thermal and mechanical performances.In order to meet the industrial requirements and obtain more useful polymeric materials,the properties of those polymeric materials must be modified.To this end,the major objective of present paper is to study the functionalization of biodegradable polymers,and only Poly-aspartic Acid?synthetic biodegradable polymeric materials?and?natural biodegradable polymeric materials?are selected to study the functionalization of the biodegradable polymers.Poly-aspartic acid,which has such many advantages as high output,industrialization producing,biodegradable and environment friendly,has been extensively studied recently as a poly-amino acid.Present paper studies poly-aspartic acidderivativesthroughgraftingmodificationandcrosslinking.Firstly,thermos-responsive poly aspartic acid derivative is discussed.Azide-functionalized poly-aspartic acid derivative P(P?HPA-Az?is synthesized using Poly-aspartic Acid as raw materials,the synthesis of prop-2-yn-1-yl phenethyl carbonate using alkynyl terminated phenethyl alcohol is studied,and the thermos-responsive polymer phe-g-P?HPA-Az?is finally synthesized by utilizing highly efficient and controllable click reaction to introduce phenethyl to the side chain of Azide-functionalized poly-aspartic acid derivative P?HPA-Az?.Then,poly-aspartic acid hydrogel?PSI-NH-SH?is synthesized using polysuccinimide and cysteamine as raw materials,and the properties of the obtained hydrogel are discussed through hydroscopicity and redox-responsive.The results show that swelling rates of hydrogel in pure water and in0.15 mMol NaCl solutions are 413 and 53,respectively.Since the thiol in cysteamine,double sulfur bands can be obtained by introducing a thiol and using oxidation linking.Under the effect of reducing agents DDT,double sulfur bands are broken through the exchange reaction of thiols so that the redox-responsive characteristic of polymer appears.The abandoned cotton linter,mainly composed of cellulose but mixed with cottonseed hull lignin and other impurities,is selected as raw material in present paper.As a consequence,impurities removal and bleaching must be conducted before functional modification.Firstly,alkali cooking,hydrogen peroxide and sodium hypochlorite bleaching are employed to deal cotton linter,and the results of impurities removal and bleaching are evaluated by dirt count and whiteness,respectively.Based on the results of impurities removal and bleaching,the optional experiment conditions are deeply discussed.Lastly,carboxymethylcellulose?CMC?is obtained through the chemical modification on the cotton linter,and degree of substitution and viscosity are used as the standard to evaluate CMC.The results show that the optional conditions of Soda-AQ cooking about cotton linter are that the alkali dosage,the highest heating temperature and the holding time are 8%,170?and 90min,respectively.The alkali dosage obviously affects the dirt count while the temperature has the most influence on yield.The mounts of one stage hydrogen peroxide bleaching and one stage sodium hypochlorite bleaching to achieve the given brightness are 3.25%and 3.0%,respectively.The two stages hydrogen peroxide and sodium hypochlorite bleaching,H_2.75P₂ can meet the requirement of bleaching of 80.03%ISO.The optional conditions of synthesis of CMC through cotton linter cellulose are that the alkali dosage,the alkalization temperature time,the dosage of etherifying agent and the time of etherifying reaction are 25%,1.5h,3g and 4h,respectively.