Intrachain Folding and Interchain Association of Hyperbranched Chains with Long Uniform Subchains Made of Amphiphilic Diblock Copolymers

Abstract

Combining atom transfer radical polymerization and copper-catalyzed azide–alkyne “click” chemistry, hyperbranched copolymers with uniform poly(tert-butyl acrylate-b-styrene-b-tert-butyl acrylate) triblock copolymer subchains, denoted as hyper-(PtBA-PS-PtBA)n, were successfully prepared and characterized by size exclusion chromatography (SEC), FT-IR, and 1H NMR. Using laser light scattering, we first studied the intrachain contraction of ultralarge hyper-(PtBA36-PS55-PtBA36)600 chains in cyclohexane, a solvent selectively poor for PS at lower temperatures. We found that at temperatures lower than 34 °C each PS block collapses into a small globule that was stabilized by its three neighboring PtBA blocks with no intrachain or interchain association in a dilute solution. Further, after hydrolyzing those tert-butyl (tBA) moieties into acrylic acids (AA), we comparatively studied the interchain association of linear triblock PAA23-PS14-PAA23 and its resultant hyper-(PAA23-PS14-PAA23)n with different overall mol...