Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550, United States.
Langmuir. 2017 May 30;33(21):5204-5212. doi: 10.1021/acs.langmuir.7b01403. Epub 2017 May 18.
Although closely related to polystyrene, poly(divinylbenzene) (PDVB) has found limited utility due to the difficulties associated with its synthesis. As a highly cross-linked polymer, PDVB is infusible and insoluble and thus nearly impossible to shape into films by either melt or solvent-based processes. Here, we report the initiated chemical vapor deposition (iCVD) of nearly stress-free, highly transparent, free-standing films of PDVB up to 25 μm thick. Films initially grow under tensile intrinsic stress but become more compressive with thickness and eventually converge to zero-stress values once they reach ≥10 μm in thickness. Upon initial heating, the evaporative loss of unreacted monomer left in the polymer matrix induces between 35 and 45 MPa of tensile stress in the films. Afterward, subsequent heating cycles induce reversible stress and film expansion behaviors. We estimate the degree of cross-linking to be 44%, resulting in high thermal stability (up to 300 °C) and mechanical stiffness (Young's modulus of 5.2 GPa). The low stress combined with high cross-linking makes iCVD PDVB an excellent candidate for protective coatings in harsh environments.
尽管与聚苯乙烯密切相关，但由于其合成困难，聚（二乙烯基苯）（PDVB）的应用有限。作为一种高度交联的聚合物，PDVB 不可熔融且不溶解，因此几乎不可能通过熔融或溶剂型工艺将其成型为薄膜。在这里，我们报告了近乎无内应力、高透明、独立的 PDVB 薄膜的引发化学气相沉积（iCVD），厚度可达 25μm。薄膜最初在拉伸固有应力下生长，但随着厚度的增加，其压缩程度增加，最终当厚度达到≥10μm 时，其应力收敛为零。在初始加热时，聚合物基质中未反应单体的蒸发损失会在薄膜中产生 35-45MPa 的拉伸应力。之后，随后的加热循环会引起可逆的应力和薄膜膨胀行为。我们估计交联度为 44%，这导致了高的热稳定性（高达 300°C）和机械刚度（杨氏模量为 5.2GPa）。低应力和高交联度使得 iCVD PDVB 成为恶劣环境下的保护性涂层的优秀候选材料。
