The birefringence of optical polymers is a great issue in optical devices, inhibiting major applications of polymers to optical lenses and films. In this study, we have synthesized effective bottlebrush polymers with which we could attain almost zero birefringence when mixed with optical poly(methyl methacrylate) (PMMA). In detail, the PMMA bottlebrush polymers (PMMA-BBP) were synthesized by the ring-opening metathesis polymerization (ROMP) of norbornene-terminated PMMA macromonomers prepared via atom transfer radical polymerization (ATRP). Linear PMMA and PMMA-BBP were mixed to fabricate blend-film samples (PMMA/PMMA-BBP), which were uniaxially drawn to introduce molecular orientations. Linear PMMA possessed a negative value for its orientation birefringence, while the value of PMMA/PMMA-BBP increased as the PMMA-BBP content increased, whose orientation birefringence could reach almost zero when the ratio of the linear PMMA to PMMA-BBP became 73:27, regardless of the magnitude of the strain. The results reveal that the orientation birefringence of PMMA can be effectively controlled and removed by blending the appropriate content of PMMA-BBP.

中文翻译：

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可控接枝链组成的瓶刷聚合物共混补偿PMMA的取向双折射

光学聚合物的双折射是光学器件中的一个大问题，阻碍了聚合物在光学透镜和薄膜中的主要应用。在这项研究中，我们合成了有效的瓶刷聚合物，当与光学聚甲基丙烯酸甲酯 (PMMA) 混合时，我们可以获得几乎为零的双折射。具体而言，PMMA 瓶刷聚合物 (PMMA-BBP) 是通过原子转移自由基聚合 (ATRP) 制备的降冰片烯封端 PMMA 大分子单体的开环复分解聚合 (ROMP) 合成的。将线性 PMMA 和 PMMA-BBP 混合以制造共混膜样品 (PMMA/PMMA-BBP)，将其单轴拉伸以引入分子取向。线性 PMMA 的取向双折射为负值，而 PMMA/PMMA-BBP 的值随着 PMMA-BBP 含量的增加而增加，当线性 PMMA 与 PMMA-BBP 之比为 73:27 时，无论应变大小如何，其取向双折射几乎可以达到零。结果表明，通过混合适当含量的PMMA-BBP，可以有效控制和去除PMMA的取向双折射。