Relationship between Morphology of Microphase-Separated Structure and Phase Restructuring at the Surface of Poly[2-hydroxyethyl methacrylate-block-4-(7‘-octenyl)styrene] Diblock Copolymers Corresponding to Environmental Change

Abstract

Hydrophilic−hydrophobic diblock copolymers composed of 2-hydroxyethyl methacrylate (HEMA) and 4-(7‘-octenyl)styrene with 26, 47, and 82 wt % of poly[4-(7‘-octenyl)styrene], HO-30, -50, and -80, respectively, were synthesized by anionic living polymerization. The surface structures of their solvent-cast films under dry and wet conditions were analyzed by contact angle measurements, transmission electron microscopic (TEM) observation, and X-ray photoelectron spectroscopic (XPS) measurements. The analytical results of HO-30 and HO-50 substantiate surface restructuring in response to environmental change. When the films were soaked in water, very quick hydration of the surface was observed. However, dehydration of the surface occurred slowly even by annealing in air. TEM observation was successfully performed by staining technique with OsO4 and introduction of a carbon−carbon double bond in the hydrophobic segment. Cross sectional TEM images of near film surfaces suggested that the phase restructuring at the outermost surface corresponding to environmental change occurred at the microdomain scale of the block copolymer. The block copolymer film of HO-80 retained a hydrophobic surface under various conditions and never experienced surface restructuring.

Living Anionic Polymerization of Functionalized Monomers, 2. Anionic Polymerization ofp-Alkenylstyrene Derivatives

“…[13] As the polymerization was not investigated in detail, some more polymerizations changing the ratios of [7] to [sec-BuLi] were carried out. In all cases, yields of polymers were quantitative.…”

“…Very recently, we [13] and Ruckenstein and Zhang [14,15] have independently reported the living anionic polymerizations of styrenes para-substituted with alkenyl groups, 8-(p-vinylphenyl)-1-octene and p-(3-butenyl)styrene whose alkenyl groups are not aryl-conjugated. The success of these living polymerizations can be supported by the fact that the addition reaction of carbanions to simple alkenes does not generally occur under normal conditions in contrast to the ready addition of carbanions to activated alkenes by aryl-conjugated such as the vinyl and isopropenyl groups of vinylbenzenes as mentioned above.…”

Dynamics of hydrated polyurethane biomaterials: Surface microphase restructuring, protein activity and platelet adhesion

“…The Nakahama group [17,18] observed surface rearrangements of a hydrophilic-hydrophobic diblock co-polymer [poly(2-hydroxyethyl methacrylate-block-isoprene)] in response to aqueous environments using transmission electron microscopy and found that the hydrophobic surface enriched with polyisoprene segments under dry conditions was replaced with poly(2-hydroxyethyl 1742-7061/$ -see front matter Ó 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.…”

Intelligent Control of Surface Hydrophobicity

“…Chen et al [99] reported a switchable copolymer with poly(vinyl sugars) as hydrophilic pendant groups on PS, in which the contact angle could be decreased by 20-408 when surfaces were soaked in water. Senshu et al [100][101][102] also demonstrated polymer rearrangement and replacement of hydrophobic groups at the uppermost surface with hydrophilic groups when soaking diblock and triblock copolymer films in water. Again, drying could be used to restore the hydrophobic surface.…”