Soft nanoparticles assembled from linear poly(ethylene glycol) and linear brush polydimethylsiloxane diblock copolymers

A series of novel amphiphilic diblock copolymers composed of hydrophilic linear poly(ethylene glycol) (PEG) and linear brush hydrophobic polydimethylsiloxane (PDMS) were synthesized. Three different molecular weights of monomethyl ether PEG were initially functionalized with 2‐bromoisobutyryl bromide to afford macroinitiators suitable for atom‐transfer radical polymerization. The macroinitiators were characterized by gel permeation chromatography, ¹H and ¹³C nuclear magnetic resonance spectroscopic analysis and matrix‐assisted laser desorption ionization time‐of‐flight mass spectroscopy. The three different molecular weight macroinitiators were then chain extended with monomethacryloxypropyl‐terminated PDMS and photoactive 2‐(methylacyloyloxy)ethyl anthracene‐9‐carboxylate in different molar ratios to afford a series of photoresponsive amphiphilic diblock copolymers with high conversions. Self‐assembly of these linear–linear brush diblock copolymers in N,N‐dimethylformamide afforded nanoparticles with hydrodynamic diameters (d_H) ranging from 41 to 268 nm, as determined by dynamic light scattering analysis. Crosslinking and stabilization of the nanoparticles was achieved via 4+4] photodimerization of the anthracene moieties upon exposure to UV radiation at 365 nm with the reverse reaction studied at a wavelength of 254 nm. Transmission electron microscopy revealed that the self‐assembled nanoparticles and their crosslinked derivatives had spherical morphologies. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1251–1262