聚丙烯-聚磷酸酯嵌段共聚物的设计与合成

以苯乙烯基团封端的聚丙烯(PP-t-St)为起始物,通过马氏加成反应将溴化氢(HBr)加成到该聚丙烯的苯乙烯双键上,得到了苄基溴基团封端的等规聚丙烯(PP-t-BzBr).以PP-t-BzBr为大分子引发剂,引发含磷烯烃单体4-乙烯基苄基膦酸二乙酯(DEVBP)的原子转移自由基聚合(ATRP),合成了一种新型聚丙烯-聚磷酸酯嵌段共聚物(PP-b-PDEVBP,其中PDEVBP嵌段质量含量可达64.3%).对该共聚物进行了1H-NMR表征、示差扫描量热(DSC)、热失重(TGA)和微型量热(MCC)分析,结果表明该嵌段共聚物在保持聚丙烯本身的熔点和结晶度的同时,有效降低了热释放速率和提高了高温热分解残余物,可望改善聚丙烯材料的阻燃性.

DESIGN AND SYNTHESIS OF POLYPROPYLENE-b-POLYPHOSPHATE BLOCK COPOLYMERS

Novel phosphorus-containing polypropylene diblock copolymers were synthesized and their thermal decomposing behaviors and flammability were characterized by thermo-gravimetric analysis(TGA) and micro-scale combustion calorimetry(MCC).First,a reactive polypropylene precursor with a terminal styryl group(PP-t-St) at polymer chain end was synthesized via controlled chain transfer reaction to 1,4-divinylbenzene and hydrogen in metallocene-mediated propylene polymerization.Then PP-t-St was reacted with hydrogen bromide through Markovnikov addition in a quasi-quantitative manner,affording 1-bromoethylbenzene group-terminated polypropylene(PP-t-BzBr).ATRP of phosphorous-containing vinyl monomer such as diethyl-(4-vinylbenzyl)phosphonate(DEVBP) was carried out in toluene at elevated temperatures with PP-t-BzBr suspending in the reactant solution,with CuCl/1,1,4,7,10,10-hexamethyltriethylenetetramine(HMTETA) as catalyst.Diblock copolymers containing different amounts of DEVBP units(up to 64.3 wt%) were obtained by adjusting polymerization durations.Differential scanning calorimetry(DSC) experiments indicated that both the crystallinity and crystallization rate of PP were largely retained in PP-b-PDEVBP diblock copolymers.TGA and MCC results showed that char residues increased while heat release rates reduced upon forming the diblock copolymers as compared to the precursory PP-t-BzBr as well as PP-t-St.Overall,this research may lead to a new solution to inherently flame-retardant polypropylene.