Strain state of poly(N-isopropylacrylamide) in polystyrene-b-poly(N-isopropylacrylamide) block copolymers and binary blends with polystyrene

• Published in: Journal of polymer science. Part B, Polymer physics Vol. 51; no. 18; pp. 1368 - 1376
• Main Authors: Rosales-Guzmán, Miguel, Alexander-Katz, Roberto, Castillo-Ocampo, Patricia, Vega-Ríos, Alejandro, Licea-Claveríe, Angel
• Format: Journal Article
• Language: English
• Published: Hoboken, NJ Blackwell Publishing Ltd 15.09.2013; Wiley; Wiley Subscription Services, Inc
• Subjects: Applied sciences; Block copolymers; Blocking; Copolymers; Cylinders; diblock copolymers; Exact sciences and technology; Morphology; Organic polymers; Physicochemistry of polymers; PNIPAM; Polymer blends; polystyrene; Polystyrene resins; Properties and characterization; Self assembly; Structure, morphology and analysis; PNIPAM; Polymer blends; polystyrene; diblock copolymers; Composition effect; Acrylamide derivative copolymer; Experimental study; Thin film; Monodispersed polymer; self-assembly; Domain structure; Morphology; Diblock copolymer; Styrene polymer; Styrene copolymer
• ISSN: 0887-6266; 1099-0488
• DOI: 10.1002/polb.23342

ABSTRACT Three diblock copolymers of polystyrene‐b‐poly(N‐isopropylacrylamide) (PS‐b‐PNIPAM) were prepared by reversible addition‐fragmentation chain transfer technique (RAFT) with compositions fPS = 0.84, fPS = 0.29, and fPS = 0.33. Block copolymers rich in PNIPAM were blended with polystyrene and its morphological effects were studied. The morphology of thin films was induced by acetone vapor and determined in the dried state by means of TEM. Copolymers with fPS = 0.84 and fPS = 0.29 form hexagonally packed cylinder (HPC) morphologies while that with fPS = 0.33 corresponds to a lamellar structure. In almost all cases where PNIPAM constitutes the continuous phase, a contraction of the PNIPAM blocks with respect to their average unperturbed dimension was observed, contrary to what one expects from the physics of self‐assembly of block copolymers. In contrast, for HPC morphology where PNIPAM is confined in a PS matrix, both blocks are highly extended. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1368–1376 The self‐assembly of PS‐PNIPAM diblock copolymers and their blends with polystyrene were studied; the micrographs show hexagonally packed cylinders with a continuous (right) and discrete (left) PNIPAM phase. When PNIPAM is the continuous phase, a contraction of the PNIPAM blocks compared to their average unperturbed dimensions occurs, contrary to what is expected from the physics of self‐assembly of block copolymers. In contrast, when PNIPAM is confined in a PS matrix, both blocks are highly extended.