A(x)BA(x)-type block-graft polymers with soft methacrylate middle segments and hard styrene outer grafts: Synthesis, morphology, and mechanical properties

作者：Miura Yu; Kaneko Takeshi; Satoh Kotaro; Kamigaito Masami^*; Jinnai Hiroshi; Okamoto Yoshio

来源：Chemistry-An Asian Journal, 2007, 2(5): 662-672.

DOI：10.1002/asia.200600403

• block copolymers
• mechanical properties
• nanostruetures
• polymerization
• ruthenium

Novel copolymers with controlled architectures can function as new building blocks for well-defined nanostructures on the basis of microphase separation, unlike conventional ABA triblock copolymers. A series of well-defined A(x)BA(x) type block-graft copolymers consisting of soft middle segments (dodecyl methacrylate (DMA)) and hard outer graft chains (styrene (St)) were synthesized by ruthenium-catalyzed living radical block and graft polymerization. NMR spectroscopy and size-exclusion chromatography combined with multiangle laser light scattering confirmed the well-defined structure of the A(x)BA(x) block-graft copolymers with backbones and graft chains of controlled lengths. Transmission electron microscopy and transmission electron microtomography revealed a series of morphologies for the copolymers. Morphological changes were observed from PSt "honeycomb" cylinders to lamellae and poly(DMA) cylinders with increasing PSt-graft content, whereby the phase diagram was shifted significantly to lower volume fractions of the larger-number component (St) relative to those of the corresponding ABA triblock copolymers. More specifically, poly(DMA) cylinders were observed even before the St content reached 50 wt %. The A(x)BA(x) and ABA copolymers with 17-30 wt of St exhibited characteristics of a thermoplastic elastomer with tensile strengths of 1-6 MPa and elongations at break of 70-300%. These mechanical properties can be related well to the microphase structures of the A(x)BA(x) and ABA copolymers.

• 出版日期2007