Synthesis And Structured Modification Of Block Copolymers And Formation Of Nanostructured Polymer Blends Containing Block Copolymer

A series of linear AB-type diblock copolymers and structure-modified ABA triblock copolymers were prepared via combination of reversible addition-fragmentation transfer polymerization (RAFT), macromolecular design via the interchange of xanthates (MADIX) and thiol-click chemistry. Nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC) were employed to characterize these block copolymers. These block copolymers were incoporated into thermoplastic polymers to access ordered nanostructures via self-assembly and microphase separation mechanisms. The morphology were investigated by means of transition electron microscopy (TEM), small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), fourier transform infrared spectroscopy (FTIR). The surface properties were examined by means of static contact angle analysis. The main results are being summarized as below:1. From modification of block copolymer structure to the mechanism of nanostructured blends containing polystyrene-butadiene -styreneand poly(N-vinylpyrrolidone)The polystyrene-butadiene-styrene triblock copolymer was modified via thiol-ene radical addition reaction. Nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC) were employed to prove that and SB(OH)S had been synthesized successfully. The SB(COOH)S was incorporated into PVPy. It was found that in the mixture self-organized nanophases were formed.The self-assembly behavior of blend was investigated by means of small angle X-ray scattering (SAXS), fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC),transmission electron microscopy (TEM). It was identified that the lamellar structure formed via self-assembly and microphase separation mechanisms.2. Study on the self-assembled morphology of blends containing Poly(Vinylacetate)-block-poly(N-vinylpyrrolidone) and phenoxyPoly (Vinylacetate)-block-poly (N-vinylpyrrolidone) copolymer was synthesized via the RAFT/MADIX polymerization. The multiblock copolymer was characterized by means of nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC).The PVAc-b-PVPy was incorporated into phenoxy. It was found that in the mixture microphase-separated morphology was formed.The self-assembly behavior of blend was investigated by means of small angle X-ray scattering (SAXS), fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC).3. Formation of hydrophilic microphase-separated morphology and study of thermo-responsive properties of PVPy block-containing PNIPAAm hydrogelsPoly (N-isopropylacrylamide) -block-poly(N-vinylpyrrolidone) diblock copolymer (PNIPAAm-b-PVPy) was successfully synthesized via sequential reversible addition-fragmentation transfer-macromolecular design via the interchange of xanthate (RAFT/MADIX) process.RAFT/MADIX polymerization was also employed to prepare the crosslinked poly(N-isopropylacrylamide)-graft-poly (N-isopropyl acrylamide) copolymer networks (PNIPAAm-g-PVPy). Due to the immiscibility of PNIPAAm with PVPy, the PNIPAAm-g-PVPy crosslinked copolymers displayed the microphase-separated morphology. The comb-like PNIPAAm-g-PVPy copolymer networks with PVPy as the pendent chains were characterized by means of Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS).The hydrogel behavior of PNIPAAm-g-PVPy networks was investigated in terms of swelling, deswelling and reswelling tests. With the inclusion of PVPy chains, the swelling ratios of the hydrogels were significantly enhanced compared to control PNIPAAm hydrogel. It is found that the PVPy-modified PNIPAAm hydrogels displayed faster response to the external temperature changes than control PNIPAAm hydrogel.