一端接异氰酸酯基的聚丙烯酸酯低聚物的合成及表征

用两步法合成出一端接异氰酸酯基(—NCO)的聚丙烯酸酯低聚物。首先以甲基丙烯酸甲酯(MMA)和丙烯酸丁酯(BA)为单体,巯基乙醇(2-ME)为链转移剂,低浓度的偶氮二异丁腈(AIBN)为引发剂,在110℃将按n(MMA):n(BA):n(2-ME):n(AIBN)=500:500:25:1配制的溶液,在2.5h内滴加到甲苯中,反应4h,得到多分散系数Mw/Mn=1.8、一端带羟基的聚丙烯酸酯低聚物〔(MMA—BAOH〕;再加入甲苯-2,4-二异氰酸酯(TDI)与其端羟基反应,合成出一端接异氰酸酯基的聚丙烯酸酯低聚物〔(MMA—BANCO〕。该低聚物结构与热性能用FTIR、1HNMR、13CNMR、GPC、DSC、TGA进行了表征。结果表明,产物的分子结构符合分子设计,即一端接有异氰酸酯基(—NCO),数均相对分子质量Mn在4500左右,DSC显示合成的低聚物的Tg在40℃左右,TGA测出其主要热失重在300～450℃。该低聚物可作为大分子表面改性剂,用于氮化硅、氮化铝等纳米粉体的表面修饰改性。

Synthesis and Characterization of the Monoisocyanate-terminated Low Molecular Polyacrylic Ester

A two-stage process was developed to synthesize the low molecular weight copolymer of monoisocyanate-terminated polyacrylic ester.Firstly,monohydroxyl-terminated copolymers(MMA-BA(-))OH] were synthesized from methyl methacrylate(MMA) and butyl acrylate(BA) by the radical adjusting copolymerization using a functional chain-transfer agent,2-mercaptoethanol(2-ME),and a very low initiator lever,azobisisobutyronitrile(AIBN).Solutions of 2-ME and AIBN in the monomers having a monomer/2-ME/AIBN mole ratio of 1 000/25/1 were added continuously during 2.5 h to refluxing toluene at 110 ℃.Stirring and refluxing were continued throughout the adddition for 4 h.Then,the monoisocyanate-terminated copolymers(MMA-BA(-))NCO] was obtained by the reaction of toluene-2,4-diisocynate(TDI) and (MMA-BA(-))OH.The is structure and thermal properties were characterized by ~1HNMR,~(13)CNMR,FTIR,GPC and TGA.The results showed that the molecular structure of the product in line with the advance of molecular design,which monoisocyanate-terminated polyacrylic ester was synthesised and the number-average relative molecular mass(MnTX-]) of the product is about 4 500.DSC and TGA show that there is only one T_g about 40 ℃ and the main weight loss is between 300 and 450 ℃.The oligomers can be used as the surface modifier,which was used for the surface modification of native nano-sized silicon nitride(Si_3N_4) and aluminum nitride(AlN) powder.