Synthesis Of Ultra-high Molecular Weight Poly(Methyl Methacrylate)by An Organosilane-initiated Polymerization

Poly?methyl methacrylate??PMMA?,also known as acrylic or organic glass,is an industrially important thermoplastic resin.The ordinary PMMA is flammable and has low solvent resistance and low surface hardness to resist abrasion.Stress-cracking occurs in ordinary PMMA under continuous heavy loading,leading to a limited range of application of PMMA.It is found that the heat resistance,abrasion resistance and anti-creep properties of PMMA increase with the increase of molecular weight of PMMA.For example,ultra-high molecular weight PMMA can maintain its tensile strength,bending strength and other mechanical properties over 200oC and still keeps high toughness and good abrasion-resistance.Ultra-high molecular weight PMMA is generally synthesized by either plasma polymerization or suspension polymerization.However,special equipments?e.g.,radio-frequency generators?are required for plasma polymerization.In addition,due to the complicated polymerization mechanism,the toughness and the impact resistance of PMMA from plasma polymerization are deteriorated.On the other hand,suspension polymerization often needs a large quantity of water as continuous phase and produces a lot of deflocculant-containing wastewater,resulting in low productivity,unclear transparency of polymer product and environmental concerns.This work aims to synthesize ultra-high molecular weight PMMA by an organosilane-initiated polymerization of methyl methacrylate?MMA?.The thesis primarily covers the following aspects:1.An ultra-high molecular weight PMMA has been prepared via an organosilane-initiated polymerization of MMA.The effects of MMA/initiator molar ratio,the types of catalyst and initiator,and the reaction atmosphere on the molecular weight of PMMA were investigated.An ultra-high molecular weight PMMA with a number-average molecular weight as high as 4.18?10⁶ Da,a weight-average molecular weight as high as 5.52?10⁶ Da,and a polydisepersity index of 1.32 was obtained under optimal reaction conditions.2.The MMA/initiator molar ratio,the type of the catalyst and initiator,and the reaction temperature were found to have a great influence on the dependence of PMMA molecular weights on reaction time.With the increase of monomer conversion,the number-average of PMMA increased linearly from 34320 Da to224050 Da in the reaction system containing DPS as an initiator and 0.1‰CP relative to monomer amount as a catalyst under the atmosphere of N₂.The results suggested that the reaction system was featured with characteristics of“living”/controlled polymerization.3.A kinetic investigation of the polymerization demonstrated that the polymerization rate followed a first-order kinetics with respect to monomer concentration.The polymerization had an apparent activation energy 126.84 kJ/mol with a pre-expotional factor of 1.15×10¹88 min^-1.