ABSTRACT
The influence of ZnO nanoparticles on the thermal degradation behavior of poly(methyl methacrylate) (PMMA) was tested using thermoanalytical techniques. The studied materials were investigated using TG, DTA, EGA, XRD, SEM and TEM. The ZnO nanoparticles were synthesized via precipitation by adding LiOH into Zn2+ water/ethylene glycol solutions. The ZnO-PMMA nanocomposites were prepared by adding the appropriate amount of ZnO into MMA and subsequent MMA radical polymerization. According to the experimental results and model-free isoconversional activation energy calculations, the addition of ZnO into PMMA played a double role. The ZnO concentrations up to 0.15% stabilized the composite by shifting the degradation interval toward higher temperatures and increasing the apparent activation energy relative to pure PMMA. At higher concentrations, the catalytic effect of ZnO started to prevail and was reflected in the lower temperature intervals of intense PMMA degradation and lower apparent activation energy. The addition of ZnO generally did not change the nature of the PMMA decomposition process.
ABSTRACT
We investigated the efficiency of poly(methyl methacrylate)-b-poly(methacrylic acid) (PMMA-b-PMAA) diblock copolymers as reactive polymeric surfactants for the functionalization of ZnO nanoparticles (NPs) of diameters ranging from 20 to 80 nm. PMMA-b-PMAA with molar masses in the range of 20.000 and 30.000 g/mol and PMAA content between 3 and 30 mol % were prepared by reversible addition-fragmentation chain transfer (RAFT) radical polymerization. Scanning transmission electron microscopy (STEM) showed efficient coverage of the particle surface with a polymer layer and infrared (IR) spectroscopy provided evidence of interaction of the PMAA segment (anchoring chains) with the NP surface. As demonstrated by dynamic light scattering (DLS) and UV-vis spectroscopy, the amphiphilic PMMA-b-PMAA block copolymers prevented agglomeration of ZnO NPs to great extent and thus increased transparency of ZnO suspensions in tetrahydrofuran (THF) and PMMA/ZnO nanocomposites in the visible light region. We also demonstrated the importance of the length of PMAA segment for ZnO surface functionalization. Optimal UV-vis performance of suspensions of functionalized NPs in THF as well as of PMMA/ZnO nanocomposites was achieved with PMMA-b-PMAA block copolymers containing 3 and 15 mol % of anchoring PMAA segment.
ABSTRACT
We present a simple, low-temperature synthesis of pure ZnO nanoparticles and polymer-ZnO hybrid materials formed by the NaOH-mediated conversion of poly(zinc dimethacrylate) in 1-butanol. The polymer poly(zinc dimethacrylate) was used as a precursor to prepare neat ZnO particles. It has a double role in the ZnO formation process, acting as a template and simultaneously controlling the crystal growth. The obtained single-crystalline ZnO nanorods show a low tendency to aggregate. The reaction mechanism of ZnO formation was proposed on the basis of a model system of the base-mediated conversion of a monomer zinc dimethacrylate Zn(MA)(2).
