官能化聚四氢呋喃-b-聚异丁烯-b-聚四氢呋喃三嵌段共聚物的合成与性能

采用2-氯-2,4,4-三甲基戊烷或对二枯基氯为引发剂和TiCl4或FeCl3为共引发剂,引发异丁烯(IB)可控/活性正离子聚合与官能端基转化,设计合成不同分子量及窄分子量分布的端基官能化聚异丁烯,如双端烯丙基溴官能化聚异丁烯(Br-PIB-Br)或双端烯丙基胺官能化聚异丁烯(H2N-PIB-NH2).采用烯丙基溴/高氯酸银体系引发四氢呋喃(THF)开环聚合,合成聚四氢呋喃活性链(PTHF+).进一步通过将IB可控/活性正离子聚合与THF可控/活性正离子开环聚合2种方法相结合,设计合成2种新型官能化聚四氢呋喃-b-聚异丁烯-b-聚四氢呋喃(PTHF-b-PIB-b-PTHF)三嵌段共聚物:(1)以上述Br-PIB-Br为大分子引发剂,在AgClO4作用下引发THF活性正离子开环聚合,采用水终止活性链端,设计合成双端为羟基的HO-PTHF-b-PIB-b-PTHF-OH三嵌段共聚物(简称:FIBF-OH);(2)以上述合成的PTHF+活性链与H2NPIB-NH2链端胺基发生高效亲核取代反应,设计合成中间链段连接点含―NH―官能基团的PTHF-b-HNPIB-NH-b-PTHF三嵌段共聚物(简称:FIBF-NH).在上述三嵌段共聚物中,极性PTHF链段与非极性PIB链段的热力学不相容,导致其呈现明显的微相分离,且微观形态与共聚组成相关.PTHF均聚物易结晶,在上述共聚物中由于PTHF链段单端受限致其结晶性减弱.三嵌段共聚物分子链的中间连接点含―NH―官能基团,具有更强的氢键作用,促进PTHF链段重排并结晶,易形成更紧密的超分子网络结构,导致即使在PTHF链段相对分子量为0.7 kg·mol^-1时仍具有较强的结晶性,且结晶熔融温度明显提高.此外,由于FIBF-NH中形成超分子网络结构,使材料具有优异的自修复性能,材料表面的切痕在常温下10 min后可以完全自愈合.本文设计合成的新型官能化PTHF-b-PIB-b-PTHF三嵌段共聚物兼具有PTHF与PIB的优良性能,在生物医用、智能修复等功能材料领域具有潜在的应用前景.

Synthesis and Property of Novel Functionalized Polytetrahydrofuran-b-polyisobutylene-b-polytetrahydrofuran Triblock Copolymers

The functionalized polyisobutylenes(PIBs)carrying allyl-Br or allyl-NH2 with different molecular weights and narrow molecular weight distribution,could be successfully synthesized via controlled/living cationic polymerization of isobutylene(IB)in n-hexane/CH2Cl2 mixed solvents at-80℃.Controlled/Living cationic ringopening polymerization(ROP)of tetrahydrofuran(THF)was achieved with Allyl-Br/AgClO4 initiating system at 0℃.Two kinds of novel functionalized PTHF-b-PIB-b-PTHF triblock copolymers were designed and synthesized via combination with controlled/living cationic polymerization of IB and controlled/living cationic ROP of THF.Terminal hydroxyl functionalized HO-PTHF-b-PIB-b-PTHF-OH triblock copolymers(expressed as FIBF-OH)were successfully synthesized by using the PIBs with difunctional allyl-Br terminal groups(Br-PIB-Br)as macroinitiators to initiate living cationic ROP of THF in the presence of AgClO4 to create living PTHF+-b-PIB-bPTHF+chains and then terminating by H20 molecules.On the other hand,PTHF-b-HN-PIB-NH-b-PTHF triblock copolymers containing hydrogen bonds at the connection point of PTHF and PIB segments(expressed as FIBFNH)were also successfully synthesized via efficient nucleophilic substitution reaction between living PTHF+chains and amine groups in H2 N-PIB-NH2.Due to the dynamic incompatibility between polar PTHF segments and nonpolar PIB segments and the crystallization of PTHF segments,PTHF-b-PIB-b-PTHF triblock copolymers exhibit an obvious microphase separation micromorphology.It is recognized that the chemical structure in the PTHF-b-PIB-b-PTHF triblock copolymers makes a great contribution to the formation of hydrogen bonding and thus the supramolecular network.The crystallization of PTHF segments could be improved even in FIBF-NH with relatively short PTHF segments,e.g.Mn,PTHF=0.7 kg·mol^-1.FIBF-NH could be completely self-healing at 25℃ for 10 min after cutting on its surface.However,the cutting on FIBF-OH surface was difficult to heal even at 30℃ for 3 days.Moreover,the PTHF-b-PIB-b-PTHF triblock copolymers could be used as drug carrier by interactions between PTHF segment and drug.The drug carrier microspheres exhibit pH-sensitive drug-release rate in PBS with different pH values.The novel functionalized PTHF-b-PIB-b-PTHF triblock copolymers combined the respective good properties from PIB and PTHF segments would have their potential applications as biomedical and smart-healing functional materials.