Abstract
Poly(2-(methacryloyloxy)ethyl phosphorylcholine)-b-poly(N,N-diethyl acrylamide) (PMPCm-PDEAn) was synthesized via reversible addition-fragmentation chain transfer (RAFT) controlled radical polymerization. Below, the critical aggregation temperature (CAT) the diblock copolymer dissolved in water as a unimer with a hydrodynamic radius (Rh) of ca. 5 nm. Above the CAT the diblock copolymers formed polymer micelles composed of a PDEA core and biocompatible PMPC shells, due to hydrophobic self-aggregation of the thermo-responsive PDEA block. A fluorescence probe study showed that small hydrophobic small guest molecules could be incorporated into the core of the polymer micelle above the CAT. The incorporated guest molecules were released from the core into the bulk aqueous phase when the temperature decreased to values below the CAT because of micelle dissociation.
Highlights
Phospholipids are a component of lipid bilayers in cell membranes; they are of interest in the biochemical and biomedical fields as unique substrates
Thermo-responsive diblock copolymers were prepared via reversible addition-fragmentation chain transfer (RAFT) controlled/living radical polymerization
Diblock copolymers, composed of hydrophilic biocompatible poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC) blocks of the same degree of polymerization (DP) (= 64) and thermo-responsive PDEA blocks with different DPs (= 22, 35, 46, and 66), were synthesized
Summary
Phospholipids are a component of lipid bilayers in cell membranes; they are of interest in the biochemical and biomedical fields as unique substrates. Lowe et al [8] reported the synthesis of diblock copolymers (PMPCm-PDEAn) composed of hydrophilic PMPC and thermo-responsive PDEA blocks and investigated their thermo-responsive association behavior in water using NMR and dynamic light scattering (DLS) measurements. We were interested in the detailed thermo-responsive association behavior of PMPCm-PDEAn and the potential for controlled release of guest molecules, such as drugs, in the cores of polymer micelles. We focused on diblock copolymers based on a hydrophilic shell-forming PMPC block and a thermo-responsive core-forming PDEA block (Figure 1). When the temperature is elevated above LCST, the PDEA block becomes hydrophobic because of the breaking of hydrogen bonding interactions between the pendant amide bond in the PDEA block and water molecules, leading to the formation of micelles with a dehydrated PDEA core and hydrated. These polymer micelles can incorporate in their hydrophobic core hydrophobic guest molecules, such as pyrene and adriamycin hydrochloride (ADR)
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