【摘要】 用2,4-甲苯二异氰酸酯(TDI)对以外消旋乳酸(D,L-LA)直接熔融聚合合成的低分子量聚外消旋乳酸(PDLLA)进行扩链,用粘均分子量、红外光谱(IR)、核磁共振氢谱(1H NMR)、DSC、X-射线衍射等对扩链产物进行了表征。在SnCl2催化下,NCO/OH=1,160℃下反应60min,可得到Mη为扩链前3.42倍的可溶性聚乳酸类生物降解材料。IR1、H NMR表明熔融聚合-TDI熔融扩链产物引入了NH和苯环,DSC、XRD等表征发现扩链使Tg、Tm和结晶度等相应提高。但是,温度过高、时间过长、NCO/OH过大时,易生成可溶性差的交联副产物,较多副产物的混杂会导致Tg和结晶性的降低。更多还原

【Abstract】 Starting from cheaper D,L-lactic acid（D,L-LA）,lower molecular weight poly（D,L-lactic acid）（PDLLA） was directly synthesized via melt polycondensation.And then,using PDLLA as prepolymer,and 2,4-toluylene diisocyanate（TDI） as chain extender,poly（D,L-lactic acid）s biodegradable material was synthesized through diisocyanate chain extension in melt state.Catalyzed by SnCl₂,under the chain extension conditions,including NCO/OH molar ratio 1.0,temperature 160℃ and time 60min,viscosity-average molecular weight（M_η） of chain extension product dissolvable in chloroform could be 3.42 times higher than before.The structure of the product extended by TDI was characterized with FTIR and（）¹H NMR.And the chain extension product（TDI-PDLLA） had higher glass transition temperature（Tg）,melting temperature（Tm）,and crystallinity than prepolymer PDLLA.However,cross-linking by-products with worse solubility in chloroform was apt to be produced once the reaction temperature was higher,or the reaction time was longer, or the molar ratio of NCO/OH was bigger.The existence of more cross-linking by-products made the Tg and crystallinity of TDI-PDLLA decrease.更多还原