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A x BA x ‐Type Block–Graft Polymers with Soft Methacrylate Middle Segments and Hard Styrene Outer Grafts: Synthesis, Morphology, and Mechanical Properties
Author(s) -
Miura Yu,
Kaneko Takeshi,
Satoh Kotaro,
Kamigaito Masami,
Jinnai Hiroshi,
Okamoto Yoshio
Publication year - 2007
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.200600403
Subject(s) - copolymer , materials science , thermoplastic elastomer , polymer chemistry , transmission electron microscopy , polymer , methacrylate , styrene , polymerization , elastomer , small angle x ray scattering , composite material , scattering , nanotechnology , optics , physics
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.