Synthesis of hyperbranched polyacrylates using self-condensing vinyl polymerization (SCVP) atom transfer radical polymerization (ATRP) by diverse initiation techniques in aqueous dispersed systems.

摘要

A major thrust of polymer research in both industry and academia is being driven by the push for sustainable raw materials, environmentally friendly production processes and products that are biodegradable. Hyperbranched polyacrylates were synthesized by atom transfer radical polymerization by self-condensing vinyl polymerization (ATRP-SCVP) using a new class of inimers based on a naturally occurring amino acid, L-serine. The structure of these hyperbranched polyacrylates (HP) includes an ester group at the branch points and in the polymer backbone of many of the repeat units, which provide sites for biodegradation via hydrolysis. In contrast to previous studies, which were performed in bulk or solution and took long periods of time to reach high molecular weight (M n), we synthesized our hyperbranched polyacrylate using emulsions and mainly miniemulsions polymerization techniques. This provides an environmentally friendly system, high number average molecular weight in the range of 10 5 to 106 Da, particle size distribution in the range of 50 to 500 nm, high functionality and high reactivity rate. The emulsion and/or miniemulsion conditions that were performed include normal ATRP, reverse ATRP, simultaneous reverse normal initiation SRNI-ATRP, and activator generated by electron transfer AGET-ATRP.;The physical and chemical properties of the hyperbranched polyacrylates were studied in detail by 1H, and 13C 1D nuclear magnetic resonance (NMR) spectroscopies. The molecular weights were determined by gel permeation chromatography using light scattering (GPCLS) and reflactive index (GPCPSt) detectors. Thermal properties, such as glass transitions and melting temperatures were determined by differential scanning calorimetry, and the morphology by scanning electron microscopy (SEM). Emulsions and miniemulsions that were sonicated in OMNOVA were analyzed by traditional test methods, including particle size average distribution (number and volume) by DLS (nanotrac), surface tension energy, pH, thermal transition, number average molecular weight Mn, weight average molecular weight Mw and molecular weight distribution (PDI). The rheological properties of these latexes were evaluated using a Brookfield viscometer.;The presence of branching in the hyperbranched polyacrylates was analyzed using 2D NMR spectroscopy based on heterogeneous and homogenous techniques such as 1H-1H COSY, 1H- 1H TCOSY, 1H-13C HMBC and 1H- 13C HSQC NMR. Finally biodegradation studies from these samples were followed by degradation procedures previously reported in our group.;This dissertation's results provided us with a better option to produce hyperbranched polyacrylates with a high degree of functionality, in a single-pot, in aqueous conditions controlling molecular weight, and particle size distribution maintained colloidal stable miniemulsions.