Title

Tuning Nanostructure Morphology and Gold Nanoparticle "Locking" of Multi-Responsive Amphiphilic Diblock Copolymers

Document Type

Article

Publication Date

4-28-2009

Department

Polymers and High Performance Materials

Abstract

Reversible addition-fragmentation chain transfer (RAFT) polymerization was utilized to prepare multiresponsive, self-assembling amphiphilic poly [(N,N-dimethylaminoethyl methacrylate)(x)-b-(N-isopropylacrylamide)(y)] (DMAEMA(x)-b-NIPAM(y)). Controlling block lengths, solution pH, and NaCl concentration to elicit changes in the hydrophilic mass fraction resulted in specific. morphological changes upon thermally induced assembly. At y = 102 (68 wt % DMAEMA), DMAEMA(165)-b-NIPAM(102) Copolymers self-assemble into simple core-shell micelles (58 nm). Increasing y to 202 (48 wt % DMAEMA) leads to a mixture of spherical micelles (78 nm) and worm-like micelles (D = 50-100 nm, L = 400-500 nm). Further increasing y to 435 (36 wt % DMAEMA) produces vesicular structures (179 nm). Significantly, reversible assembly of these nanostructures from the present stimuli-responsive diblock copolymers can be accomplished directly in aqueous media without the necessity of dialysis or manipulation with cosolvents. Additionally, the associated nanostructures can be shell cross-linked above the critical aggregation temperature via the in situ formation of gold nanoparticles yielding assemblies with long-term aqueous stability.

Publication Title

Macromolecules

Volume

42

Issue

8

First Page

2958

Last Page

2964