Molecular weight dependence of the growth rate of spherulite of cyclic poly(ε-caprolactone) polymerized by ring expansion reaction
Molecular weight dependence of the growth rate of spherulite of cyclic poly(ε-caprolactone) polymerized by ring expansion reaction
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DOI：
10.1016/j.polymer.2020.122403
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发表时间：
2020-04
期刊：
影响因子：
4.6
通讯作者：
Ryogo Ono;Hironori Atarashi;S. Yamazaki;K. Kimura
中科院分区：
文献类型：
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作者：
Ryogo Ono;Hironori Atarashi;S. Yamazaki;K. Kimura
为了阐明扩环反应合成的环状聚合物球晶生长速率（G）与分子量（Mw）的关系，采用偏光显微镜研究了结晶温度（Tc）和过冷度（ΔT）对环状聚己内酯（C-PCL）球晶生长速率（G）的影响。制备了分子量分别为17000、33000、41000、74000和85000的C-PCL和分子量分别为16000、35000和60000的线型PCL（L-PCL），其中分子量是用线型聚苯乙烯为标准品通过GPC测定的，并对所有样品进行了Gobey方程G= G 0 exp（-B/TΔT）计算。C-PCL的二次成核活化能（B）除分子量最低的C-PCL外，其余均相同。由于B与次级核的端面自由能成正比，这意味着高分子量的C-PCL的折叠表面的规则性与分子量无关，在相同的T ΔT下，与分子量几乎相同的C-PCL和L-PCL相比，L-PCL的G要高于C-PCL。这表明，C-PCL和L-PCL的G不是由缠结单独控制的，因为C-PCL的缠结低于L-PCL。我们发现了以下关联：C-PCL的G 0 = Mw− 1.2，L-PCL的G 0 = Mw− 0.67。G 0依赖于MW的幂次的差异反映了在次级核中进行滑动扩散的困难。这有力地支持了生长前沿次级核中C-PCL链的吸收行为与L-PCL的吸收行为显著不同的假设。
To elucidate the molecular weight (Mw) dependence of the growth rate of spherulite (G) of cyclic polymers polymerized by the ring expansion reaction, we studied theGof cyclic poly(ε-caprolactone) (C-PCL) growing from the melt as a function of the crystallization temperature (Tc) and degree of supercooling (ΔT) using polarizing optical microscopy. We prepared C-PCLs comprising an exclusively repeating unit, excluding other structural units withMw= 17000, 33000, 41000, 74000 and 85000 and linear PCLs (L-PCL) withMw= 16000, 35000 and 60000, whereMwwas determined by GPC using linear polystyrene standards.Gobeyed the equation,G=G0exp(−B/TΔT), for all the samples. The activation energies of secondary nucleation (B) of C-PCL were almost identical except for the C-PCL with the lowestMw. SinceBis proportional to the end surface free energy of the secondary nucleus, it implies that the regularity of the folding surface of C-PCL with highMwis independent ofMw.Compared to C-PCL and L-PCL having almost the sameMw,Gof L-PCL is higher than that of C-PCL at the sameTΔT. This suggests thatGof C-PCL and L-PCL is not solely controlled by the entanglement because the entanglement of C-PCL is lower than that of L-PCL. We found the following associations:G0∝Mw−1.2for C-PCL andG0∝Mw−0.67for L-PCL. The difference in the power of theG0dependence onMwreflects the difficulty of performing sliding diffusion in the secondary nucleus. This strongly supports the hypothesis that the absorption behavior of C-PCL chains in the secondary nucleus on the growth front is significantly different from that of L-PCL.