聚甲基丙烯酸甲酯和聚碳酸酯各向异性光学性质理论研究

作为重要的光学薄膜材料，聚甲基丙烯酸甲酯(PMMA)和聚碳酸酯(PC)在诸多工业领域已得到广泛应用.本文利用密度泛函理论结合分子动力学方法深入系统地研究了这两种聚合物的各向异性光学性质，并对比分析了不同分子链长度和微观结构对其各向异性光学性质的影响.计算结果表明PMMA和PC都具有较高的本征双折射率，且分子链长度对本征折射率的影响显著.在可见光范围内，单体单元PMMA本征双折射率在10%以上，而三单元结构本征折射率则不到4%.对于体相结构多聚体，从立方结构拉伸到厚度仅有6?的过程中，PC不同方向折射率最大差异高达6%,而同样情况下PMMA不同方向折射率差异仅有1.3%.此项研究有助于理解PMMA和PC聚合物各向异性光学特征产生的原因和影响因素，从而进一步指导和促进其在更多领域的发展与应用.

Theoretical calculation of the anisotropic optical properties of poly-methyl methacrylate and polycarbonate

As important optical film materials, polymethyl methacrylate (PMMA) and polycarbonate (PC) have achieved the wide application in many industrial fields. In this work, the anisotropic optical properties of these two polymers were systematically studied, and the effects of different molecular chain lengths and microstructures on their anisotropic optical properties were compared by using density functional theory combined with molecular dynamics methods. Our results indicate that both PMMA and PC have high intrinsic birefringence, and the length of the molecular chain has a significant influence on the intrinsic refractive index. In the visible light range, the intrinsic birefringence of PMMA monomer unit is more than 10%, while that of PMMA trimer unit is less than 4%. For bulk structure polymers, during the process of stretching from a cubic structure to a thickness of only 6 Å, the maximum difference in refractive index in different directions of PC is as high as 6%, whereas the difference of PMMA is only 1.3% in the same case. This work may provide extensive insights into the causes and influence factors of the anisotropic optical characteristics of PMMA and PC polymers, so as to further guide and promote their development and application in more fields.