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首页> 外文期刊>RSC Advances >Diblock copolymers composed of a liquid crystalline azo block and a poly(dimethylsiloxane) block: synthesis, morphology and photoresponsive properties
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Diblock copolymers composed of a liquid crystalline azo block and a poly(dimethylsiloxane) block: synthesis, morphology and photoresponsive properties

机译：由液晶偶氮嵌段和聚二甲基硅氧烷嵌段组成的二嵌段共聚物：合成，形态和光响应性能

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摘要

A series of diblock copolymers, composed of a soft poly(dimethylsiloxane) (PDMS) block with a defined length and a liquid crystalline poly(6-(4-(4'-cyanophenylazo) phenoxy) hexyl acrylate) (POCN) block with different lengths, was synthesized by the atom transfer radical polymerization (ATRP). A homopolymer POCN was also prepared by the same method for comparison. The polymer structures, liquid crystalline phase, microphase-separated morphology, and photoisomerization were then investigated by H-1 NMR, FT-IR, GPC, UV-Vis, POM, DSC, XRD and TEM. The results showed that the well-defined diblock copolymers (PDMSn-b-POCNm) possess four different soft/rigid ratios (n = 58, m = 8, 15, 24, 36) and relatively narrow molecular distributions (PDI <= 1.30). POCN blocks of the copolymers form a smectic-A sub-phase, which is identical to the mesomorphic behaviour of POCN. After being annealed at 140 degrees C in a vacuum for 24 h, the copolymers form a lamellar morphology when WPDMS is 42.3-57.8% and a morphology of PDMS spheres embedded in an azo matrix when WPDMS is 23.3-31.4%. POCN and PDMSn-b-POCNm in solution show typical photoisomerization behaviour of the azobenzene moieties. Although H-aggregation is observed to a certain extent, photochemical processes of the as-cast films of the polymers are similar to those of the solutions. On the other hand, the photoisomerization behaviour of annealed PDMSn-b-POCNm films is significantly different from that of the annealed POCN film, which is closely correlated with the phase-separated morphologies. The observations can provide deep understanding of the phase-separated structures and be used to develop new materials.
机译：一系列二嵌段共聚物，由具有限定长度的软聚二甲基硅氧烷（PDMS）嵌段和液晶聚（6-（4-（4'-氰基苯基偶氮）苯氧基）丙烯酸己酯）（POCN）嵌段组成通过原子转移自由基聚合（ATRP）合成长度。还通过相同方法制备均聚物POCN用于比较。然后通过H-1 NMR，FT-IR，GPC，UV-Vis，POM，DSC，XRD和TEM研究了聚合物的结构，液晶相，微相分离的形态和光异构化。结果表明，定义明确的二嵌段共聚物（PDMSn-b-POCNm）具有四种不同的软/刚性比（n = 58，m = 8，15，24，36）和相对窄的分子分布（PDI <= 1.30） 。共聚物的POCN嵌段形成近晶A子相，与POCN的同构行为相同。在真空中在140摄氏度下退火24小时后，当WPDMS为42.3-57.8％时，共聚物形成层状形态;当WPDMS为23.3-31.4％时，共聚物形成嵌入偶氮基体中的PDMS球状形态。溶液中的POCN和PDMSn-b-POCNm显示出偶氮苯部分的典型光异构化行为。尽管在一定程度上观察到H-聚集，但是聚合物的铸态膜的光化学过程与溶液的那些相似。另一方面，退火的PDMSn-b-POCNm薄膜的光异构化行为与退火的POCN薄膜的光异构化行为显着不同，这与相分离的形态密切相关。这些观察结果可以提供对相分离结构的深刻理解，并可以用于开发新材料。

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