Fast and solvent‐free microwave‐assisted synthesis of thermoresponsive oligo(glycidyl ether)s

Abstract

Low‐molecular weight linear poly(glycidyl ether)s are typically synthesized via the “classical,” oxy‐anionic ring‐opening polymerization (ROP) of glycidyl ether monomers at elevated temperatures. To reduce reaction times, a fast process was developed to synthesize oligo(glycidyl ether)s (OGEs) in bulk at a gram‐scale utilizing microwave heating. Well‐defined thermoresponsive copolymers comprising glycidyl methyl ether and ethyl glycidyl ether with molecular weights of up to 3 kDa were synthesized via microwave‐assisted ROP with reaction times of approximately 10 min. The fast reaction kinetics were attributed to the rapid and uniform heating and high temperatures reached during the reaction. Consequently, no significant microwave‐specific acceleration of the oxy‐anionic ROP was observed. The temperature‐triggered phase transition of the OGEs in aqueous solution revealed cloud point temperatures that are highly dependent on the OGE molecular weight, concentration, and comonomer composition, which extends previously reported data. Furthermore, oligo(glycidyl ether) acrylates (OGEAs) with reactive, functional end groups were directly accessible via in situ quenching of the anionic, microwave‐assisted ROP with acrylic acid chloride. The obtained thermoresponsive OGEA macromonomers represent a promising material for the functionalization of surfaces via radical grafting methods to obtain functional, thermoresponsive coatings with potential application in cell culture. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 2496–2504

Thermoresponsive Poly(glycidyl ether) Brush Coatings on Various Tissue Culture Substrates—How Block Copolymer Design and Substrate Material Govern Self-Assembly and Phase Transition

“…Due to this LCST-type phase transition, such PGEs are soluble in aqueous media below a critical temperature, whereas they undergo a coil-to-globule transition to form turbid solutions when the temperature is raised above their so-called cloud point temperature (CPT). Similar to various POx and POEGMA copolymers [ 42 , 43 ], the CPT of thermoresponsive PGEs can be adjusted via the GME:EGE comonomer ratio and the sharp phase transition is fully reversible and exhibits little to no thermal hysteresis [ 19 , 39 , 40 , 44 ]. In addition, PGEs exhibit a concentration-dependent as well as a strongly molecular weight-dependent CPTs in the range between 1 and 30 kDa [ 39 , 44 ].…”

Grafting Density-Dependent Phase Transition Mechanism of Thermoresponsive Poly(glycidyl ether) Brushes: A Comprehensive QCM-D Study

“…Generally, a clear downward trend of CPTs with increasing polymer molecular weight is observed. 28,33 Here, the 2-iminothiolane anchor group might cause additional polymer aggregation in water and shift the CPT to lower values due to higher apparent polymer molecular weight. Similar observations were made for PGE copolymers with a hydrophobic benzophenone anchor block.…”

Switchable Oligo(glycidyl ether) Acrylate Bottlebrushes “Grafted-from” Polystyrene Surfaces: A Versatile Strategy toward Functional Cell Culture Substrates

“…32,33 However, in one of our recent reports we have shown that low molecular weight oligo(glycidyl ether)s (OGEs) based on glycidyl methyl ether (GME) and ethyl glycidyl ether (EGE) exhibit a temperature-dependent phase transition in aqueous solution and can be conveniently endfunctionalized into oligo(glycidyl ether) acrylates (OGEAs, Scheme 1a). 38 This class of macromonomers has already been utilized to functionalize gold model substrates via SI-ATRP to yield nonresponsive, protein-resistant bottlebrush coatings. 34 On that account, the aim of this work was to develop a method for the UV-induced radical photografting of OGEAs from PS culture dishes to obtain thermoresponsive bottlebrush coatings and to explore their potential as functional tissue culture substrates for the temperature-triggered fabrication of cell sheets.…”

“…Synthesis of thermoresponsive OGEA macromonomers of various molecular weights was performed as reported recently. 38 Briefly, the two glycidyl ether monomers GME and EGE were polymerized via anionic ROP to yield oligomers of 0.5 and 1 kDa with PDIs of 1.2−1.3. Subsequent acrylation yielded the respective OGEA macromonomers.…”

“…34 Apart from the just mentioned report, surface-initiated "grafting-from" macromonomer methods have been limited to dual-functional antimicrobial/antibiofouling bottlebrush coatings developed by Su, Gao, Zhi et al, who grafted macromonomers based on poly(ethylene glycol) (PEG)polycation block copolymers from argon plasma-activated poly(dimethylsiloxane) substrates using UV-induced free radical polymerization. 35−37 Herein, we applied thermoresponsive oligo(glycidyl ether) acrylate (OGEA) macromonomers which are accessible in one-pot via the convenient oxy-anionic ROP of glycidyl methyl ether (GME) and ethyl glycidyl ether (EGE) under solventfree conditions as recently reported 38 for surface coating. We established an efficient "grafting-from" macromonomer approach to yield thermoresponsive OGEA bottlebrushes on PS culture substrates via surface-initiated free radical photografting for further use in cell culture.…”