丙烯与1,3-丁二烯配位共聚合制备兼具高刚性与高韧性的嵌段共聚物

Block Copolymers with High Rigidity and Toughness Prepared via Coordination Copolymerization of Propylene with 1,3-Butadiene

以二甲基吡啶胺铪/[Ph_(3)C][B(C_(6)F_(5))_(4)]/AliBu_(3)为催化体系,通过一锅两步法在温和条件下制备了一系列高分子量、窄分子量分布且具有高等规度的等规聚丙烯(iPP,硬段)与丙烯-1,3-丁二烯(1,3-BD)无规共聚物(软段)的嵌段共聚物.通过高温核磁(^(1)H-NMR、^(13)C-NMR)、高温凝胶渗透色谱(GPC)、示差扫描量热法(DSC)、动态力学分析(DMA)和拉伸力学性能测试,对所制备嵌段聚合物的结构和性能进行了分析表征.结果表明,1,3-BD以1,2-和trans-1,4-2种方式无规插入共聚物分子链中,且以trans-1,4-插入方式为主;共聚物具有较高的熔融温度(T_(m)约为158℃)和极低的玻璃化转变温度(T_(g)可达−70℃).独特的软-硬结构赋予材料优异的力学性能:共聚物同时具有较高的拉伸强度(≥33 MPa)和断裂伸长率(最高为800%).以上研究结果表明,通过调节软硬段的结构,可以高效制备兼具高刚性与高韧性的iPP嵌段共聚物,结合的丙烯与1,3-BD无规共聚物软段是对全同PP进行增韧改性非常有效的手段.

A series of propylene/1,3-butadiene(BD)block copolymers with high molecular weight(>1.3×10^(5))and narrow molecular weight distribution(1.8~2.0)were prepared via“one-pot,two-step”method by using dimethylpyridine amine hafnium/[Ph_(3)C][B(C_(6)F_(5))_(4)]/AliBu_(3) as catalyst system under mild conditions.By Varying the reaction time for each step and BD dosage in the second step,the block length of each block and composition of the soft block could be easily tuned.Molecular weight and molecular weight distribution,thermal properties,microstructure and mechanical properties of the obtained block copolymers were clearly characterized by high temperature gel chromatography(GPC),differential scanning calorimetry(DSC),high temperature nuclear magnetic(NMR),tensile test,etc.The block copolymers contain both a hard iPP block and soft propylene/BD random copolymer block.It was revealed that 1,3-BD was randomly inserted into the molecular chain via both 1,2-and trans-1,4-insertion manners,and the amount of the latter was about six times that of the former.The copolymers showed high melting temperature(T_(m)≈158℃)and very low glass transition temperature(Tg around−70℃).The obtained block copolymers with both hard iPP segments and propylene/1,3-BD random copolymer block helped to achieve both high rigidity and toughness simultaneously.As proved,the block copolymers showed high tensile strength(≥33 MPa)and elongation at break(up to 800%).The above results indicated that via tuning the hard and soft block composition during the two-step copolymerization of propylene and BD,block copolymers with much improved tensile properties could be easily obtained.Incorporation of a very soft propylene-BD random copolymer block plays a vital role in iPP toughening.The research results will provide new idea for the development of the iPPs with excellent mechanical properties.