Novel, self-associating hybrid copolymers were synthesized via controlled ring-opening polymerization of N-carboxyanhydride of Z-L-lysine (Z-L-Lys-NCA), initiated by amino-functional macroinitiators. A poly(N-isopropy...Novel, self-associating hybrid copolymers were synthesized via controlled ring-opening polymerization of N-carboxyanhydride of Z-L-lysine (Z-L-Lys-NCA), initiated by amino-functional macroinitiators. A poly(N-isopropylacry-lamide) (PNIPAm)-based macroinitiator containing 10 mol% of polyoxyethylene grafts and a terminal primary amine group in the form of ammonium hydrochloride (PNIPAm-g-PEО) was synthesized and used to initiate the ammonium- mediated ring-opening polymerization of NCA described by Dimitrov and Schlaad [1]. Thus, hybrid copolymers ((PNIPAm-g-PEO)-b-PLys) with controlled molar-mass characteristics and functionality were obtained. The potential applications of PNIPAm-based copolymers in the systems for controlled drug release, immobilization of enzymes and protein purification have aroused great interest in the studies of their properties and behaviour. The thermal stability and thermodynamic properties of the copolymers obtained were studied. The differential thermal analysis of polyfunctional hybrid copolymers (PNIPAm-g-PEO)-b-PLys) showed that thermooxidative destruction occurs in two stages: primary, of the unstable fragments (grafted chains of PEO);and secondary, of the main polymer chains of poly(N-isopropylacry-lamide) and poly(L-lysine). The kinetics of thermal degradation was evaluated and the values of the activation energy of the degradation process, changes of Gibbs free energy, enthalpy and entropy for the formation of the activated complex were also calculated.展开更多
Tri-block amphiphilic copolymers with hybrid architectures were synthesized by coupling linear （poly（ethylene） glycol）（PEG） and dendritic second-generation Fréchet-type poly（benzyl ether）（PBE） via the W...Tri-block amphiphilic copolymers with hybrid architectures were synthesized by coupling linear （poly（ethylene） glycol）（PEG） and dendritic second-generation Fréchet-type poly（benzyl ether）（PBE） via the Williamson reaction （Gisotv,et al. Angew Chem,Int Ed Engl,1992,31:1200～1202）.Our experimental study shows that the powerful two-dimensional （）1H- （）13C heteronuclear multiple-quantum correlation （HMQC） and two-dimensional （）1H- （）13C heteronuclear multiple-bond correlation （HMBC） NMR techniques rather than the classical one-dimensional （）1H and （）13C-NMR methods can provide clear evidence to verify the formation of the tri-block copolymers.In our measurements HMQC and HMBC NMR techniques directly detected the signal of ether bonds bridged in-between PBE dendrons and PEG blocks,therefore,the formation of the block copolymers are evidently confirmed in molecular level.This work also provides a general method to exactly confirm the formation of block copolymers.展开更多
文摘Novel, self-associating hybrid copolymers were synthesized via controlled ring-opening polymerization of N-carboxyanhydride of Z-L-lysine (Z-L-Lys-NCA), initiated by amino-functional macroinitiators. A poly(N-isopropylacry-lamide) (PNIPAm)-based macroinitiator containing 10 mol% of polyoxyethylene grafts and a terminal primary amine group in the form of ammonium hydrochloride (PNIPAm-g-PEО) was synthesized and used to initiate the ammonium- mediated ring-opening polymerization of NCA described by Dimitrov and Schlaad [1]. Thus, hybrid copolymers ((PNIPAm-g-PEO)-b-PLys) with controlled molar-mass characteristics and functionality were obtained. The potential applications of PNIPAm-based copolymers in the systems for controlled drug release, immobilization of enzymes and protein purification have aroused great interest in the studies of their properties and behaviour. The thermal stability and thermodynamic properties of the copolymers obtained were studied. The differential thermal analysis of polyfunctional hybrid copolymers (PNIPAm-g-PEO)-b-PLys) showed that thermooxidative destruction occurs in two stages: primary, of the unstable fragments (grafted chains of PEO);and secondary, of the main polymer chains of poly(N-isopropylacry-lamide) and poly(L-lysine). The kinetics of thermal degradation was evaluated and the values of the activation energy of the degradation process, changes of Gibbs free energy, enthalpy and entropy for the formation of the activated complex were also calculated.
文摘Tri-block amphiphilic copolymers with hybrid architectures were synthesized by coupling linear （poly（ethylene） glycol）（PEG） and dendritic second-generation Fréchet-type poly（benzyl ether）（PBE） via the Williamson reaction （Gisotv,et al. Angew Chem,Int Ed Engl,1992,31:1200～1202）.Our experimental study shows that the powerful two-dimensional （）1H- （）13C heteronuclear multiple-quantum correlation （HMQC） and two-dimensional （）1H- （）13C heteronuclear multiple-bond correlation （HMBC） NMR techniques rather than the classical one-dimensional （）1H and （）13C-NMR methods can provide clear evidence to verify the formation of the tri-block copolymers.In our measurements HMQC and HMBC NMR techniques directly detected the signal of ether bonds bridged in-between PBE dendrons and PEG blocks,therefore,the formation of the block copolymers are evidently confirmed in molecular level.This work also provides a general method to exactly confirm the formation of block copolymers.
