Abstract
High molecular weight water-soluble polymers are widely used as flocculants or thickeners. However, synthesis of such polymers via solution polymerization invariably results in highly viscous fluids, which makes subsequent processing somewhat problematic. Alternatively, such polymers can be prepared as colloidal dispersions; in principle, this is advantageous because the particulate nature of the polymer chains ensures a much lower fluid viscosity. Herein we exemplify the latter approach by reporting the convenient one-pot synthesis of high molecular weight poly(glycerol monomethacrylate) (PGMA) via the reversible addition–fragmentation chain transfer (RAFT) aqueous emulsion polymerization of a water-immiscible protected monomer precursor, isopropylideneglycerol methacrylate (IPGMA) at 70 °C, using a water-soluble poly(glycerol monomethacrylate) (PGMA) chain transfer agent as a steric stabilizer. This formulation produces a low-viscosity aqueous dispersion of PGMA–PIPGMA diblock copolymer nanoparticles at 20% solids. Subsequent acid deprotection of the hydrophobic core-forming PIPGMA block leads to particle dissolution and affords a viscous aqueous solution comprising high molecular weight PGMA homopolymer chains with a relatively narrow molecular weight distribution. Moreover, it is shown that this latex precursor route offers an important advantage compared to the RAFT aqueous solution polymerization of glycerol monomethacrylate since it provides a significantly faster rate of polymerization (and hence higher monomer conversion) under comparable conditions.
Highlights
Water-soluble polymers can be used for a wide range of commercial applications, including as flocculants in brewing,[1] for dewatering in paper manufacture[2−4] or for municipal water purification.[5−7] High molecular weight (>105 g mol−1)polymers are efficient and include nonionic, anionic, or cationic polyacrylamides,[7−9] poly(ethylene oxide) (PEO),[10] and poly(diallyldimethylammonium) chloride (PDADMAC).[11]
Poly(glycerol monomethacrylate) (PGMA) is a watersoluble polymer that is highly biocompatible and nonfouling and has been utilized for the manufacture of soft contact lenses.[23−25] Glycerol monomethacrylate (GMA) is a relatively expensive specialty monomer. It can be obtained via hydrolysis of a cheap commodity monomer, glycidyl methacrylate, in aqueous solution,[26] but in practice it is prepared via a protected precursor, isopropylideneglycerol methacrylate.[27]
Canton et al demonstrated that human stem cell colonies enter stasis within 16 h of their immersion within poly(glycerol monomethacrylate) (PGMA)-based block copolymer worm gels.[33]
Summary
Water-soluble polymers can be used for a wide range of commercial applications, including as flocculants in brewing,[1] for dewatering in paper manufacture[2−4] or for municipal water purification.[5−7] High molecular weight (>105 g mol−1)polymers are efficient and include nonionic, anionic, or cationic polyacrylamides,[7−9] poly(ethylene oxide) (PEO),[10] and poly(diallyldimethylammonium) chloride (PDADMAC).[11]. Poly(glycerol monomethacrylate) (PGMA) is a watersoluble polymer that is highly biocompatible and nonfouling and has been utilized for the manufacture of soft contact lenses.[23−25] Glycerol monomethacrylate (GMA) is a relatively expensive specialty monomer In principle, it can be obtained via hydrolysis of a cheap commodity monomer, glycidyl methacrylate, in aqueous solution,[26] but in practice it is prepared via a protected precursor, isopropylideneglycerol methacrylate.[27] In the field of biomaterials, GMA-based copolymers have been used to prepare hydrogels that act as corneal substitutes,[28] for the design of amphiphilic networks that serve as suitable substrates for dermal fibroblasts,[29−31] and grown in the form of a hydrophilic brush layer from tissue culture polystyrene in order to improve cell adhesion.[32] Canton et al demonstrated that human stem cell colonies enter stasis within 16 h of their immersion within PGMA-based block copolymer worm gels.[33] In addition, the cis-diol moiety of Received: February 7, 2018 Revised: March 27, 2018 Published: April 16, 2018
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