Synthesis and supramolecular self‐assembly of thermosensitive amphiphilic star copolymers based on a hyperbranched polyether core

Abstract

A novel amphiphilic thermosensitive star copolymer with a hydrophobic hyperbranched poly (3‐ethyl‐3‐(hydroxymethyl)oxetane) (HBPO) core and many hydrophilic poly(2‐(dimethylamino) ethyl methacrylate) (PDMAEMA) arms was synthesized and used as the precursor for the aqueous solution self‐assembly. All the copolymers directly aggregated into core–shell unimolecular micelles (around 10 nm) and size‐controllable large multimolecular micelles (around 100 nm) in water at room temperature, according to pyrene probe fluorescence spectrometry and 1H NMR, TEM, and DLS measurements. The star copolymers also underwent sharp, thermosensitive phase transitions at a lower critical solution temperature (LCST), which were proved to be originated from the secondary aggregation of the large micelles driven by increasing hydrophobic interaction due to the dehydration of PDMAEMA shells on heating. A quantitative variable temperature NMR analysis method was designed by using potassium hydrogen phthalate as an external standard and displayed great potential to evaluate the LCST transition at the molecular level. The drug loading and temperature‐dependent release properties of HBPO‐star‐PDMAEMA micelles were also investigated by using indomethacin as a model drug. The indomethacin‐loaded micelles displayed a rapid drug release at a temperature around LCST. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 668–681, 2008

Self‐Assembly of Hyperbranched Polymers and Its Biomedical Applications

“…[ 131 ] in water at room temperature. [ 129 ] Furthermore, these micelle solutions underwent sharp, thermosensitive phase transitions at the lower critical solution temperature (LCST). Mechanism studies indicated with the increase of temperature, the large and the release rate increases in the acidic medium due to the acid-cleavable hydrazone linkage.…”

Polycationic star polymers with hyperbranched cores for gene delivery

“…Hyperbranched poly(3-ethyl-3-(hydroxymethyl)oxetane (HBPO) functionalized with bromoester or trithiocarbonate moieties has been used to synthesize PDMAEMA stars by ATRP [25][26][27] and reversible addition fragmentation polymerization [28]. In addition, Yan et al [29] studied the anionic polymerization of DMAEMA using hydroxyl terminated HBPO, reacted with potassium hydride, as the macroinitiator.…”

Miktoarms hyperbranched polymer brushes: One-step fast synthesis by parallel click chemistry and hierarchical self-assembly

“…After the polymers were totally resolved overnight, a certain amount of n-hexane (newly distilled) was added into the solution until white turbidity appears. After keeping the samples still for at least half an hour, the hydrodynamics radius (R h ) of the self-assembly structure was measured by DLS at 25 °C [41], followed by making the self-assembly samples by the spin-coating method on freshly-peeled mica substrates for AFM measurements afterwards.…”