Catalytic, Sulfur-Free Chain Transfer Agents That Alter the Mechanical Properties of Cross-Linked Photopolymers
Catalytic, Sulfur-Free Chain Transfer Agents That Alter the Mechanical Properties of Cross-Linked Photopolymers
复制标题
可改变交联光聚合物机械性能的催化无硫链转移剂
DOI：
10.1021/jacs.3c03811
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发表时间：
2023
影响因子：
15
通讯作者：
Worrell, Brady T.
中科院分区：
文献类型：
--
作者：
Bagnall, Nicholas R.;Jones, Meredith H.;Jernigan, G. Cole;Routt, Chase;Dar, Lisa C.;Worrell, Brady T.
由光聚合产生的热固性材料经常遭受明显的收缩应力，通常是脆性的，并且具有有限的机械性能。各种类型的链转移剂（cta）已经被研究和开发出来，通过终止链和原位引发新的链来降低光聚合物的交联密度。尽管cta成功地控制了光聚合物的机械性能，但它们在聚合过程中通常会被消耗，因此需要高负载（高达总配方的20%）。此外，传统的cta通常含有硫，这是有气味的，可以产生不稳定的配方。这里介绍的是一种催化的无硫CTA，它可以以ppm的量添加到现有的商业单体原料中，以产生与使用传统CTA制备的光聚合物相似的光聚合物，但负载低10 000倍。这些基于大环钴酰肟的催化剂被发现可以根据催化剂的负载可调地降低链的分子量。结果表明，仅使用商业单体，该催化剂可以在相同的加工条件下降低玻璃化转变温度（Tg），橡胶模量（E ' rubber）和交联光聚合物的刚度，并保持99.99%的配方相同。
Thermosetting materials generated by photopolymerization frequently suffer from significant shrinkage stress, are often brittle, and have a limited range of mechanical properties. Various classes of chain transfer agents (CTAs) have been investigated and developed to reduce the cross-linking density of photopolymers by terminating chains and initiating new chainsin situ. Although CTAs are successful in manipulating the mechanical properties of photopolymers, they are traditionally consumed during the polymerization and are therefore required in high loadings (up to 20 wt % of the total formulation). Moreover, traditional CTAs frequently contain sulfur, which is malodorous and can create unstable formulations. Presented here is a catalytic, sulfur-free CTA that can be added in ppm quantities to existing commercial monomer feedstocks to create photopolymers similar to those prepared using traditional CTAs, but at 10 000-fold lower loadings. These catalysts, which are based on macrocyclic cobaloximes, were found to tunably reduce the molecular weight of the chain proportional to catalyst loading. It was shown, using only commercial monomers, that this catalyst could reduce the glass-transition temperature (Tg), rubbery modulus (E′rubbery), and stiffness of a cross-linked photopolymer while utilizing identical processing conditions and keeping 99.99 wt % of the formulation the same.