Synthesis And Study On The Functional Polymers Containing Heteroatom Sidechains Modified By Nano Chalcogenide

The study of polymer nanocoposites (PNCs) focus on their mechanical, thermal, tribological, optical transparency, luminescence, magnetic, electrical and catalytic properties. In the present work, some functional polymers and their nanocomposites have been prepared, such as thiol-functional polystyrene/CdS (TPSC), polystyrene-b-poly(4-vinylpyridine)/ML (M=Cd, Zn; L=S, Se) (PS4VP/ML), poly(N-phenylmaleimide-b-4-vinylpyridine)/ML(M=Cd,Zn;L=S,Se)(PNPMI-b-P4VP/ML), poly(N-phenylmaleimide-b-dimethylamino methacrylate)/ML(M=Cd, Zn; L=S, Se) (PNPMI-b-PDMAM/ML), poly(3-alkylthiophene)/MS(M=Cd, Zn) (P3ATs/MS) and poly(3-alkoxythiophenes) (P3AOTs). The combination of nanoparticles with polymers can promote the stability and fluorescence yield of materials, also their nonlinear optics performance. The optical properties of PNCs are related to the structure of composites, which determined by the size and dispersion of nanoparticles. To control the composition of polymer, the content and size of nanoparticles, also the structure of PNCs, the radical polymerization (RP) and reversible addition-fragmentation chain transfer (RAFT) methods have been used to synthesize the functional polymers, then the corresponding PNCs were prepared by in-situ method.1. Synthesis of the TPSC and study on the method to control the content and size of CdS in the composites. The composition of polystyrene-co-polychloromethylstyrene can be determined by the styrene-to-chloromethylstyren ratio during copolymerization, then the thiol content is determined. The CdS concentration is also changed through different thiol-to-CdCl₂ ratio. The crystal styles of CdS in the TPSC are also changed from cubic to hexagonal with increasing CdS content. The PL properties of TPSC are promoted by the CdS nanoparticles, which having quantum effect. The PL mainly comes from CdS. 2. PS4VP/CdS (ZnS, CdSe) have been prepared by RAFT polymerization using 4VP/M²⁺ as monomers for the first time. The composition, molecular weight and their dispersion of polymers are controlled well by living polymerization. The tunable crystal styles of CdS (from cubic to hexagonal) and optical properties of PNCs also have been realized. The nanoparticles tend to congregate together with the increasing polymeric time, resulting in the growth of nanoparticles and the self-assembly of PNCs. The morphology of PNCs are also changed from nanofilms, nanorods, netholes to nanowires by changing the concentration of PNCs, the content of nanoparticles, the environment temperature or the solvent for dispersion of composites. The legend-centered charge-transfer (LCCT) and LMCT mechanism coexist in the PNCs containing a small quantity of nanoparticles. However, the LMCT is the dominant mechanism in the PNCs with a high content of nanoparticles i.e. the LCCT tends to convert to LMCT when the concentration of nanoparticles increases. The photoluminescence properties of PNCs are tuned up by ZnS, CdS and CdSe nanoparticles, and some white light PNCs such as PS4VP/ZnS/CdS/CdSe were obtained.3. The PNPMI-b-P4VP/CdS(ZnS, CdSe) and PNPMI-b-PDMAM/CdS(ZnS, CdSe) PNCs have been prepared by RAFT polymerization using 4VP/M²⁺ and DMAM/M²⁺ as monomers for the first time. The composition, molecular weight and their dispersion of polymers are controlled well by living polymerization. The obtained PNCs have tunable crystal styles of nanoparticles and optical properties of PNCs. The nanoparticles tend to congregate together with the increasing polymerization time, resulting in the growth of nanoparticles and the self-assembly of PNCs. The morphology of PNCs are also varied by changing the concentration of PNCs, the content of nanoparticles, the environment temperature or the solvent for dispersion of composites. The ligand-centered charge-transfer (LCCT) and LMCT mechanism coexist in the PNCs containing a small quantity of nanoparticles. However, the LMCT is the dominant mechanism in the PNCs with a high content of nanoparticles i.e. the LCCT tends to convert to LMCT when the concentration of nanoparticles increases. The photoluminescence (PL) properties of PNCs are tuned up by ZnS, CdS and CdSe nanoparticles, and some white light PNCs such as PNPMI-b-P4VP/ZnS/CdS/CdSe and PNPMI-b-PDMAM/ZnS/CdS/CdSe were obtained. The NLO absorption and refraction of PNCs are also strong, resulting from the interaction between the nanoparticles and the polymers.4. P3ATs and P3AOTs were synthesized by chemical oxidation and the P3ATs/MS(M=Cd, Zn) were prepared by in-situ method. The effect of alkyl sidechains on the regioregularity and the optical properties of P3ATs were studied, respectively. The dependence of PL and NLO properties of PNCs on the nanoparticles also introduced. The ratio of head-to-tail (HT) coupling in the P3ATs decreases with the carbon number of sidechains increasing from 3 to 12, combing with a blue shift of absorption and a stronger PL intensity. The NLO properties and conductivity of P3ATs with a larger alkyl group decrease. The LMCT and LCCT coexist in the P3ATs/MS, and also are changeable. Interestingly, the excited wavelength and emission peaks of poly(3-dodecyl thiophene)/CdS (P3DDT/CdS) could not be changed by changing the CdS content. This is assigned to the valence band offset is larger than their conduction band offset, so, the electron-hole recombination mainly occurred in the P3DDT. The NLO performance of P3ATs/MS are better than that of P3ATs. The surface-induced charge separation (i.e. the coherent oscillation of the conduction band electrons) is expected to enhance the anisotropic polarization and hence the nonlinear optical response.