Libraries of Statistical Hydroxypropyl Acrylate Containing Copolymers with LCST Properties Prepared by NMP
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Eggenhuisen, Tamara M.; Becer, C. Remzi; Fijten, Martin W. M.; Eckardt, Rebecca; Hoogenboom, Richard; Schubert, Ulrich S.
- Abstract:
- The nitroxide-mediated copolymerization of 2-hydroxypropyl acrylate (HPA) with N-acryloylmorpholine
(Amor) or N,N-dimethylacrylamide (DMA) was investigated using N-tert-butyl-N-(1′-diethylphosphono-
2,2′-dimethylpropyl)-O-(2-carboxyl-prop-2-yl) (BlocBuilder) alkoxyamine initiator and additional free nitroxide
(SG-1). Different reaction conditions, such as the concentration of additional SG-1, were tested to optimize the
homopolymerizations using a Chemspeed ASW2000 automated parallel synthesizer. Best control for the
homopolymerizations (polydispersity indices of 1.2-1.3) of all three monomers was achieved using 20% additional
SG-1 (relative to the initiator) at a reaction temperature of 110 °C for 2 M solutions in N,N-dimethylformamide
and a monomer/initiator ratio of 100/1. Libraries of P(Amor-stat-HPA) and P(DMA-stat-HPA) were synthesized
with 0-100 mol % HPA with 10 mol % increments using the optimized conditions obtained for the
homopolymerizations. The resulting polymers had narrow molecular weight distributions, and their compositions,
determined using 1H NMR spectroscopy and elemental analysis, were close to the theoretical compositions. In
addition, all copolymers of both libraries had single glass transition temperatures (Tg), and the transition temperatures
decreased from the Tg of P(Amor) (147 °C) and P(DMA) (111 °C) to the Tg of P(HPA) (22 °C) with increasing
HPA content. The cloud point of P(HPA) showed concentration dependence as well as a concentration dependent
hysteresis. The cloud points of aqueous solutions of the copolymer libraries could be tuned from 21.4 to 88.0 °C
and to 82.9 °C for P(Amor-stat-HPA) and P(DMA-stat-HPA), respectively, at a concentration of 1 wt %. LCST
behavior was observed for copolymers with >40 wt % HPA in P(Amor-stat-HPA) and >55 wt % HPA in the
P(DMA-stat-HPA) library.
- Year:
- 2008
- Type of Publication:
- Article
- Journal:
- Macromolecules
- Volume:
- 41
- Pages:
- 5132 - 5140