含树枝化以及线性侧链的超分子共聚物的液晶相结构调控

Mesomorphic Phase Behaviour of Hydrogen-bonded Supramolecular Copolymers Containing Dendritic and Linear Side Chains

设计了一类由聚4-乙烯基吡啶(P4VP)、含弯曲树枝化分子12CBP以及线性分子PDP组成的三元共混体系,其中12CBP和PDP端基均为酚羟基,可与P4VP侧基的吡啶环上的N原子进行氢键复合.傅立叶变换红外光谱、示差扫描量热法、偏光显微镜、小角X射线散射和原子力显微镜等多种研究表明该共混体系为均相体系,三组分自组装形成以P4VP为主链,12CBP和PDP为超分子侧链的"无规共聚物"P4VP(12CBP)x(PDP)y(x+y=1).该超分子侧链共聚物的聚集态结构与小分子12CBP和PDP相对含量有关.当12CBP含量x≥0.5时,体系组装形成六方柱状相结构,柱子的直径随着体系中12CBP含量减少而逐渐减小.当12CBP含量<0.5时,即使少量12CBP的引入也会引起体系层状相结构的破坏,体系表现为无定形状态.

The self-assembled structure, from hydrogen-bonded copolymers containing poly（4-vinylpyridine） （P4VP）, linear surfactant pentadecylphenol （PDP） and dendritic molecules, 1-[4＇-（3＂,4＂,5＂-tridecyloxy- benzoyloxy）phenyleneoxycarbonyl]-3-[（4＂-hydroxyphenyl）oxycarbonyl]benzene （12CBP）, was investigated. The ternary complex system is named as P4VP（12CBP）x（PDP）y （x ＋ y = 1） which was prepared via solution blending method. It has been reported that P4VP（12CBP）x possess hexagonal columnar structure at x 〉 0.3 and P4VP（PDP）x possess lamellar structure. Despite the different shapes and self-assembled properties from 12CBP and PDP, FTIR, DSC, POM and SAXS studies revealed that the temary supramolecular copolymer system forms a homogeneous phase, instead of phase separation. At x 〉 0.5, P4VP（12CBP）x（PDP）y possesses a homogeneous hexagonal columnar phase. Each column is constructed with P4VP as polymer backbone tethered with mixed side chains. The lattice parameter is smaller than that of the corresponding P4VP（12CBP）x＋y and decreases gradually with decreasing x. In this case, the P4VP polymer chains are surrounded by 12CBP and PDP molecules which would induce ＂defects＂ from shape difference of the molecules. While the results show that such kind of＂defects＂ didn＇t prevent the columnar phase formation. The formation of each column with randomly distributed 12CBP and PDP would increase the system entropy. Meanwhile, smaller PDP provides more free volume, especially in alkoxy segment, and further increases the conformational entropy of the side chains. At x 〈 0.5, P4VP（12CBP）x（PDP）y is amorphous with layer like fluctuation, instead of columnar phase. In this case, the relative grafting density of the linear side chains is larger than that of dendritic side chains, which could not stabilize the columnar phase formation. Meanwhile the existence of small amount of 12CBP tends to interrupt the lamellar mesophase formation. AFM topographies of P4VP（12CBP）x（PDP）y thin films also support the formation of homogeneous phase. The typical fingerprint patterns from hexagonal columnar phase are gradually interrupted with decreasing x. At x 〈 0.5, only irregular morphology could be detected. So the surface pattems of such kind of supramolecular copolymer thin films could be easily controlled by varying x and y.