Study On Syn Thesis Of Met Hacrylate-based Polymers,Preparation Of Related Composites And Optical Properties Of The Resultant Products

Photoresponsive polymer materials can respond to the external light stimuli by altering reversibly their physical and chemical properties. Therefore, photoresponsive polymer materials have important applications in optically rewritable data storage materials, anti-forgery materials, optical limiting materials, chemical sensing and biomaterials.Herein, three series of photoresponsive methacrylate-based block copolymers and a kind of polymethylmethacrylate composites containing multi-walled carbon nanotube/metal phthalocyanines hybrid with optical limiting effects were synthesized or prepared. Their structures or composite were characterized and their photoresponsive behaviors or optical limiting effects were studied.Four groups of novel azobenzene-containing block copolymers (PMMA-b-P(BMA-co-AzoMA)) with different block ratios (69/31,57/43,23/77 and 28/72) were synthesized by atomic transfer radical polymerization (ATRP). These block copolymer thin films were obtained by spin-coating on the silicon substrates. Upon annealing treatments, the surface morphologies in those copolymer films were observed by atomic forced microscopy (AFM) in tapping mode. These polymer films exhibited dewetting-induced island, rodlikeor bicontinuous stripes structures dependent on the films thickness. Photoisomerization of azobenzene units in the films controlled by UV irradiation and thermal effects in the dark lead to the reversible transformation of surface morphologies between island and bicontinuous stripes. Phase separation occurred between PMMA phase with higher polarity and P(BMA-co-AzoMA) phase with lower polarity. The P(BMA-co-AzoMA) phase was apt to distribute on the film surface and PMMA adhered on the substrate. The photoisomerization of azobenzene units by UV irradiation would change the wetting behaviors of surface layer P(BMA-co-AzoMA) on the underling PMMA layer. Therefore, the surface dewetting morphologies on the film were controlled by UV light.Two kinds of amphiphilic block copolymers containing photochromic spiropyran units P(BMA-co-SPMA)-b-PDMAEMA with different molecular weights (9.6×103 and 1.27 × 104) were synthesized by ATRP method. The photoresponsive behaviors and luminescences of the copolymer P(BMA-co-SPMA)-Br in THF, DMF and toluene solution were studied by UV/Vis absorption spectra and fluorescent emission spectra. The effects of the solvent polarity on the photochromic and luminescence were discussed. Then the self-assembly behaviors of the amphiphilic block copolymers P(BMA-co-SPMA)-b-PDMAEMA in water were studied. The block copolymer self-assembled into micelle observed by TEM images. The hydrophilic PDMAEMA block formed the micelle shell and hydrophobic P(BMA-co-SPMA) formed the micelle core. The diameters of the polymer micelles in different temperatures and pH values were investigated by dynamic laser scattering. Upon UV irradiation, the polymer micelles exhibited intense fluorescence as well as photochromic behaviors. The fluorescence intensity of merocyanine was strengthen because the spiropyran units were restricted into the hydrophobic micelle core. The paper coated with the polymer micelle also exhibited intense pink fluorescence, which could be switched by photoisomerization of spiropyran controlled by UV and visible irradiation.Two kinds of ABA-type tri-block copolymers containing spiropyran units PDMAEMA-b-P(BMA-co-SPMA)-b-PDMAEMA with different molecular weights (1.82×104 and 2.08×104) were synthesized by ATRP method. The recognizing abilities of copolymer Br-P(BMA-co-SPMA)-Br film to metal ions were studied by UV/Vis absorption spectra. The copolymer Br-P(BMA-co-SPMA)-Br films showed different colors when exposed to different metal ions. The self-assembly behaviors of amphihilic tri-block copolymers in water were studied by virtue of TEM. It was observed that the two kinds of copolymers formed micelle structures, in which the hydrophilic PDMAEMA block formed the micelle shell and hydrophobic P(BMA-co-SPMA) formed the micelle core. The photoresponsive behaviors and luminescences of the copolymer Br-P(BMA-co-SPMA)-Br in solution were studied by UV/Vis absorption spectra and fluorescent emission spectra. The diameters of the polymer micelles in different temperatures and pH values were investigated by dynamic laser scattering. The polyacrylic acid (PAA) films doped with micelles exhibited intense pink fluorescence as well as photochromic behaviors. Besides, these PAA films showed thermochromism behaviors. And the color of the PAA films changed from red to pink when increasing the temperature until the color faded completely.Multi-walled carbon nanotubes purified by two-steps method were noncovalently functionalized with copper phthalocyanines (CuPc), cobalt phthalocyanines (CoPc), and nickel phthalocyanines (NiPc), zinc phthalocyanines (ZnPc) and iron phthalocyanines (FePc) respectively by π-π stacking method. The MPcs molecules layers stacked on the MWNT were observed by TEM. And the content of MPcs in each hybrid was investigated by TGA. The interactions between MWNT and MPcs molecules in the hybrid were studied by UV/Vis absorption spectra. Compared with individual MPcs, the hybrid had broader absorption and showed red-shift behaviors, which was attributed to the expanded conjugated delocalized area in the hybrid. Refluxing in concentrated nitric acid was used to purify MWNT and carboxylic groups (-COOH) were produced on the MWNT. The effects of-COOH on the π-π stacking of MPcs were studied based on MWNT/CuPc hybrid. MWNT, CuPc and MWNT/CuPc were introduced into polymethyl methacrylate (PMMA) matrixes and three kinds of composites MWNT/PMMA, CuPc/PMMA and MWNT/CuPc/PMMA were obtained. The influences of composites thicknesses and doptant contents in the PMMA matrixes on the transmissions of the PMMA composites were studied. Under same concentration, the transmission of CuPc/PMMA composite was biggest and MWNT/PMMA composite was smallest. The optical limiting effects of three hybrids MWNT/CoPc, MWNT/NiPc, MWNT/ZnPc solution and three kinds of PMMA composites were studied by virtue of 1064nm laser produced by Nd:YAG laser instrument. The output intensities of each MWNT/MPcs solutions were smaller than those of MWNT or MPcs solutions under same concentration. The hybrids solutions exhibited better optical limiting responses and the limiting ability of MWNT/ZnPc composite was best among three kinds of hybrids. The output energy intensities of the PMMA composites decreased generally with increasing the dopant contents in the matrix. When the weight ratio of CuPc was 1.9×10-2%, the output energy intensity began to increase slowly above 223mJ/cm2 and the composite showed optical limiting responses. MWNT/PMMA composites did not show obvious optical limiting effects below 100mJ/cm2 when the concentrations of MWNT in the composites increased from 0.5×10-2% to 1.9×10-2%. However, the output energy intensities of MWNT/CuPc/PMMA composites began to increase slowly at lower concentration (0.5×10-2%) and smaller input energy intensities (65-70mJ/cm2) than other two kinds of composites. MWNT/CuPc/PMMA composites exhibited better optical limiting ability than other two kinds of composites.