Synthesis of Ethylene/Isoprene Copolymers Containing Cyclopentane/Cyclohexane Units as Unique Elastomers by Half-Titanocene Catalysts
Synthesis of Ethylene/Isoprene Copolymers Containing Cyclopentane/Cyclohexane Units as Unique Elastomers by Half-Titanocene Catalysts
复制标题
DOI：
10.1021/acs.macromol.2c02399
复制
发表时间：
2023-01-19
期刊：
影响因子：
5.5
通讯作者：
Nomura, Kotohiro
中科院分区：
文献类型：
--
作者：
Guo, Lijuan;Makino, Ryoji;Nomura, Kotohiro
在含酚配体的半钛茂金属催化剂Cp‘TiCl2(O-2，6-Pr-I(2)-4-R-C6H2)[Cp’=C5Me5(Cp*)，R=H(1)，SiEt3(2)的催化下，合成了玻璃化转变温度(T-g值低于-18℃)的乙烯(E)与异戊二烯(IP)共聚物。核磁共振谱的微观结构分析表明，除了已报道的催化剂中的1，4-和3，4-IP插入单元外，该共聚物还含有环戊烷(主要)和环己烷单元，这些单元是在IP和随后的乙烯插入后通过环合形成的。1，2，4-Me3C5H2类似物(R=H)表现出较好的IP掺杂率，但由于结构中环戊烷单元较少，所得E/IP共聚物具有较低的T-g值。E/IP共聚物的T-g值随IP含量的增加而增大，其程度与所用催化剂有关。由于其独特的微观结构，由1，2-MAO催化体系制备的E/IP共聚物具有良好的拉伸和弹性性能。拉伸强度先随IP含量的增加而降低，随扯断伸长率的增加而降低(IP3.3-15.6摩尔%)，然后随IP含量的进一步增加而逐渐升高(IP含量为18.1-21.5%)，断裂伸长率随着拉伸强度的保持而降低，并观察到屈服应力。
Ethylene (E) copolymers with isoprene (IP) possessing higher glass-transition temperatures (T-g values, -7.1 to 29.2 degrees C) than those prepared by the reported catalysts (T-g below -18 degrees C) have been prepared in the copolymerization by using halftitanocene catalysts containing phenoxide ligand, Cp'TiCl2(O-2,6-Pr-i(2)-4-R-C6H2) [Cp' = C5Me5 (Cp*), R = H (1), SiEt3 (2)]. Their microstructural analysis by NMR spectra revealed that the copolymers contained cyclopentane (major) and cyclohexane units, formed by cyclization after IP and subsequent ethylene insertions, in addition to 1,4- and 3,4-IP inserted units observed as major units in those prepared by reported catalysts. The 1,2,4-Me3C5H2 analogue (R = H) showed better IP incorporation, but the resulting E/IP copolymers possessed rather low T-g values compared to those prepared by 1,2 due to less cyclopentane unit in the microstructure. The T-g value in the E/IP copolymer increased upon the increase of the IP content, and the degree was dependent upon the catalyst employed. Due to their unique microstructure, the resulting E/IP copolymers prepared by 1,2-MAO catalyst systems exhibit promising tensile and elastic properties. The tensile strength initially decreased with an increase in the IP content along with an increase of the elongation at break (up to 600%, IP 3.3-15.6 mol %) and then increased gradually with further increase in the IP contents (IP 18.1-21.5 mol %); the elongation at break then decreased with preserving the tensile strength along with the observation of the yield stress.