The synthesis and self‐assembly of ABA amphiphilic block copolymers containing styrene and oligo(ethylene glycol) methyl ether methacrylate in dilute aqueous solutions: Elevated cloud point temperatures for thermoresponsive micelles

Abstract

A series of ABA amphiphilic triblock copolymers possessing polystyrene (PS) central hydrophobic blocks, one group with “short” PS blocks (DP = 54–86) and one with “long” PS blocks (DP = 183–204) were synthesized by atom transfer radical polymerization. The outer hydrophilic blocks were various lengths of poly(oligoethylene glycol methyl ether) methacrylate, a comb‐like polymer. The critical aggregation concentrations were recorded for certain block copolymer samples and were found to be in the range circa 10−9 mol L−1 for short PS blocks and circa 10−12 mol L−1 for long PS blocks. Dilute aqueous solutions were analyzed by transmission electron microscopy (TEM) and demonstrated that the short PS block copolymers formed spherical micelles and the long PS block copolymers formed predominantly spherical micelles with smaller proportions of cylindrical and Y‐branched cylindrical micelles. Dynamic light scattering analysis results agreed with the TEM observations demonstrating variations in micelle size with PS and POEGMA chain length: the hydrodynamic diameters (DH) of the shorter PS block copolymer micelles increased with increasing POEGMA block lengths while maintaining similar PS micellar core diameters (DC); in contrast the values of DH and DC for the longer PS block copolymer micelles decreased. Surface‐pressure isotherms were recorded for two of the samples and these indicated close packing of a short PS block copolymer at the air–water interface. The aggregate solutions were demonstrated to be stable over a 38‐day period with no change in aggregate size or noticeable precipitation. The cloud point temperatures of certain block copolymer aggregate solutions were measured and found to be in the range 76–93 °C; significantly these were ∼11 °C higher in temperature than those of POEGMA homopolymer samples with similar chain lengths. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7739–7756, 2008

Design of Oligo(ethylene glycol)-Based Thermoresponsive Polymers: an Optimization Study

“…In pure water, the homo-polymers PMEO 2 MA and POEGMA 300 exhibited cloud points at 28 and 65 • C, respectively. These results are in good agreement with previously reported values [26,33]. Moreover, as expected, the cloud points of the co-polymers P(MEO 2 MA-co-OEGMA 300 ) in pure water were comprised in the temperature range 28-65 • C and closely depended on the composition of the co-polymers (i.e., on F OEGMA or f OEGMA ).…”

“…The homo-polymerization of the latter monomer has been already studied by various authors. For example, Holder and co-workers recently reported that homo-polymers POEGMA 300 exhibit reversible phase transitions in aqueous solution around 60-64 • C [33]. Additionally, Ishizone and co-workers studied the anionic polymerization of tetra(ethylene glycol) methyl ether methacrylate (i.e., MEO 4 MA, one of the main component of OEGMA 300 ) and obtained homo-polymers with a LCST of 68 • C [34].…”

“…This particular category of oligo(ethylene glycol)-based macromolecules has been exponentially studied in recent years [23][24][25][26][29][30][31][32][33][34][35]. Indeed, these polymers may be synthesized using straightforward controlled radical polymerization techniques such as atom transfer radical polymerization (ATRP) [36,37] or reversible addition-fragmentation transfer polymerization (RAFT) [38][39][40], but also functionalized using versatile ligation tools such as click chemistry [41][42][43][44].…”

Hierarchically organized micellization of thermoresponsive rod‐coil copolymers based on poly[oligo(ethylene glycol) methacrylate] and poly(ε‐caprolactone)

“…In this series, the chain length of the central PCL block was maintained constant and varied that of the terminal fragments. Diblock and triblock copolymers containing poly[oligo(ethylene glycol methyl ether) methacrylate] blocks have been synthesized previously 27,28 but not containing a central biodegradable block such as poly(e-caprolactone). Lately, with an increase in environmental awareness, amphiphilic biodegradable copolymers offer interesting properties for biotechnological applications.…”

Well-defined Cationic Shell Crosslinked Nanoparticles for Efficient Delivery of DNA or Peptide Nucleic Acids

“…Access to well-defined, functional block copolymers has been dramatically improved over the past decade, with the advancement of controlled radical polymerization techniques (27)(28)(29)(30)(31)(32)(33). Although polyamides having primary amino side chain substituents have been prepared directly (34) by reversible addition-fragmentation chain transfer (35,36) radical polymerization, the amphiphilic block copolymer, poly(acrylamidoethylamine)-b-polystyrene (PAEA-b-PS) used in our studies, was obtained by amidation of a common block copolymer precursor for SCK construction, poly(acrylic acid)-b-polystyrene, by reaction with mono-Boc-protected 1,2-ethylene diamine and subsequent deprotection under standard conditions.…”