The Synthesis Of Amphiphilic Conetworks Via ATRP And Click Chemistry

Amphiphilic conetworks(APCN),composed of covalently bonded,otherwise immiscible hydrophilic and hydrophobic polymer chains,can exhibit a reversible response to the change of external environment.APCN has received widespread attentions because it has broad application prospects,such as drug delivery systems,histocompatibility materials separation materials.As we all know,hydrophilic PDMAAm is physiologically inert and hydrolytic stable and hydrophobic PDMS has the highest oxygen permeability among all the polymers,both polymers are biocompatible.Therefore,an APCN consisting of PDMAAm and PDMS segments is of great interest due to its micro-phase separation and bio-compatible properties.It is important to control the uniformity of the hydrophilic segment chain length of the APCN due to the effectiveness of the biomaterials,and atom-transfer radical polymerization(ATRP)shows the versatility in the synthesis of polymers with predictable molecular weight and low polydispersity.In this article,allyl-terminated poly(dimethylacrylamide)is synthesized via atom transfer radical polymerization(ATRP)and was modified to be azide-terminated poly(dimethylacrylamide),which reacts with alkyne-terminated poly(dimethylsiloxanes)to get allyl-terminated tri-block copolymer PDMAAm-PDMS-PDMAAm via click chemistry,then PMHS is used as a crosslinker to prepare APCN.We report a novel approach to the synthesis of amphiphilic conetworks composed of PDMAAm and PDMS segments with controllable chain length through the combination of ATRP and click chemistry.The main research is descrbed as:(1)Synthesis of small molecule allyl 2-bromoisobutyrat:a new multifunctional initiator allyl 2-bromoisobutyrat,which owns allyl group and bromine atom respectively at both ends,is synthesized via cryogenic modified between allyl alcohol and 2-bromoisobutyryl.(2)Synthesis of poly(dimethylacrylamide)homopolymer through ATRP and its modification:the linear PDMAAm with a bromine end group is synthesized via ATRP,and the effect of key experimental parameters,(i.e,olven kinds,ligand kinds,reaction temperature,reaction time and feed ratios)on synthesis and properties(PDI and Mn of the polymer,monomer conversion)is studied.From the results found that the reaction system tends to form a homogeneous systemalong with the increasing polarity of solvent,which is favorable for the polymerization reaction.The relationship between molecular weight and monomer conversion rate of the polymerizationproduct shows linear relation,which meets the characteristics of active controlled polymerization.Then the bromine end group is successfully transformed to azido groups through a nucleophilicsubstitution reaction with sodium azide.(3)Synthesis of alkyne-terminated poly(dimethylsiloxane)(alkyne-PDMS-alkyne);the alkyne-terminated poly(dimethylsiloxanes)is obtained by the nucleophilic substitution reaction between propargyl bromide and OH-PDMS-OH,different reaction conditions,i.e.such as reaction temperature,catalyst kinds and the feeding molar ratios,are discussed to show their influence.(4)Preparation of tri-block copolymers copolymer PDMAAm-PDMS-PDMAAm and APCN:the allyl-terminated tri-block copolymers PDMAAm-PDMS-PDMAAm is successfully synthesized through the reaction between allyl-terminated poly(dimethylacrylamide)-N3 and alkynyl-PDMS-alkynyl via click chemistry in the presence of a CuSO4·5H2O/sodium ascorbate catalyst system.The triblock copolymer crosslinks with PHMS to get APCN.The swelling properties of APCN show that the product swells in deionized water,tetrahydrofuran and n-hexane solvents but not dissolve,which is in good agreement with the characters of APCN,and has potential as immunoproteting membranes in the bioartificial pancreas.