Well-Defined Amphiphilic Thermosensitive Copolymers Based on Poly(ethylene glycol monomethacrylate) and Methyl Methacrylate Prepared by Atom Transfer Radical Polymerization

Abstract

Amphiphilic homopolymers of the hydroxy-functional macromonomer poly(ethylene glycol) monomethacrylate (PEGMA) and its copolymers with methyl methacrylate (MMA) were prepared by atom transfer radical polymerization. Commercially available PEGMA (Aldrich) contains nonfunctional poly(ethylene glycol) (PEG), monofunctional PEGMA, and difunctional poly(ethylene glycol) dimethacrylate (PEGDMA) in a 1:3:1 ratio as analyzed by HPLC. A solvent extraction procedure yielded a PEGMA enriched mixture (PEG:PEG-MA:PEGDMA = 5:92:3) with PEGMA M n values of 480 and 410 Da based on HPLC and 1H NMR, respectively. ATRP homopolymerization of this purified PEGMA in the hydroxyl-bearing solvents, cyclohexanol and ethanol (ε = 16.4 and 25.3, respectively), yielded well-defined homopolymers (M w/M n < 1.1). On the other hand, ATRP copolymerizations with MMA (PEGMA content = 10, 18, 24, 30, and 40 mol %) yielded best results in non-hydrogen-bonding diphenyl ether (ε = 3.37). The homopolymer and copolymers containing more than 24 mol % (57 wt %) PEGMA were water-soluble and exhibited sharp lower critical solution temperatures (LCST) that increased with increasing PEGMA content as expected. Unlike similar PEGMA-based amphiphilic copolymers prepared by conventional free radical polymerizations, the ATR polymerizations reported here proceeded to high conversions (60−100%) and yielded well-defined polymers (M w/M n = 1.1−1.15) with no gel fraction that remained linear and water-soluble after storage in ambient conditions for several months.

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

“…The latter family is composed of different sub-classes. For instance, oligo(ethylene glycol)-grafted polymers based on poly(vinyl ether) [14,15], polynorbornene [16], polyester [17], polystyrene [18,19], polyacrylate [20][21][22], or polymethacrylate [23][24][25][26] backbones were all reported to exhibit a LCST in water. This thermoresponsive behavior is believed to be related to the amphiphilic character of these polymers [27,28].…”

“…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].…”

Synthesis of Fluorinated Amphiphilic Block Copolymers Based on PEGMA, HEMA, and MMA via ATRP and CuAAC Click Chemistry

“…The signal for methyl protons of -OCH 3 (a) in MMA units appeared at 3.55 ppm [38,39]. The signals of -CH 3 protons were seen at 0.88-1.36 ppm in both MMA and HEMA units, while for methylene protons they were in the range of 1.5-2.1 ppm.…”

“…The appearance of signals at 2.3-2.5 ppm and 3.38 ppm was attributed to -CH 2 and CH 3 O-protons arising from PEGMA units [39][40][41]. The methyl protons for -OCH 3 in MMA units were at 3.55 ppm, while -CH 2 O protons in PEGMA units appeared at 3.65 ppm [24,32,34].…”

“…The methyl protons for -OCH 3 in MMA units were at 3.55 ppm, while -CH 2 O protons in PEGMA units appeared at 3.65 ppm [24,32,34]. Methylene protons of -CH 2 OH in HEMA and -CH 2 in PEGMA gave a sharp signal around 4.2 ppm [38][39][40][41]. Figure 6 shows the DSC curves of P(HEMA-co-MMA) copolymers (1b and 1d), recorded between 0-180 ∘ C. A substantial decrease in the glass transition temperature with increasing HEMA content was observed, which agreed with the literature [38] : the number average molecular weight; : the weight average molecular weight.…”