Controlled (Co)Polymerization of Methacrylates Using a Novel Symmetrical Trithiocarbonate RAFT Agent Bearing Diphenylmethyl Groups

Herein, we report a novel type of symmetrical trithiocarbonate chain transfer agent (CTA) based diphenylmethyl as R groups. The utilization of this CTA in the Reversible Addition-Fragmentation chain Transfer (RAFT) process reveals an efficient control in the polymerization of methacrylic monomers and the preparation of block copolymers. The latter are obtained by the (co)polymerization of styrene or butyl acrylate using a functionalized macro-CTA polymethyl methacrylate (PMMA) previously synthesized. Data show low molecular weight dispersity values (Đ < 1.5) particularly in the polymerization of methacrylic monomers. Considering a typical RAFT mechanism, the leaving groups (R) from the fragmentation of CTA should be able to re-initiate the polymerization (formation of growth chains) allowing an efficient control of the process. Nevertheless, in the case of the polymerization of MMA in the presence of this symmetrical CTA, the polymerization process displays an atypical behavior that requires high [initiator]/[CTA] molar ratios for accessing predictable molecular weights without affecting the Đ. Some evidence suggests that this does not completely behave as a common RAFT agent as it is not completely consumed during the polymerization reaction, and it needs atypical high molar ratios [initiator]/[CTA] to be closer to the predicted molecular weight without affecting the Đ. This work demonstrates that MMA and other methacrylic monomers can be polymerized in a controlled way, and with “living” characteristics, using certain symmetrical trithiocarbonates.

Analysis of Shape and Dimensional Deformation of the Model with a Precision Circular Hole Produced by Digital Light Processing (DLP) Additive Technology

The article is about manufacturing a component with a precision circular hole by Digital Light Processing (DLP) additive technology for inserting another part. The accuracy of the hole itself depends on the choice of production technology and the appropriate material. Deformation of the inner wall of the hole prevents correct insertion of the part - nut of trapezoidal threaded rod. This article analyzes the feasibility of manufacturing a component using Digital Light Processing (DLP) additive technology and the use of liquid resin „Proto GRY“ for the manufacture a component. Among additive technologies processes, digital light processing (DLP) is typically seen as the technology capable of reaching the highest standards in terms of part complexity and precision. DLP technology rely on the use of light, typically in the UV region of the spectrum (380 – 405 nm), to cure a photosensitive viscous resin. This resin, typically composed of epoxy or acrylic and methacrylic monomers, will polymerize and harden when exposed to light. As light shines on the vat to create specific shapes or patterns that compose each layer, a solid object can be formed and extracted from the otherwise liquid resin.

Heat and weather resistance of copolymer organic glasses

The parameters of light resistance, heat resistance and water absorption of organic glasses based on methyl methacrylate copolymers with various methacrylic monomers containing UV absorbers and UV stabilizers are investigated. It has been shown that UV stabilizers - quenchers of excited states: diphenyl and isomers of terphenyl have the best stabilizing eff ect. A decrease in water absorption of copolymer organic glasses with the introduction of cyclic fragments into the copolymer was established. It was shown that the introduction of methyl methacrylate - methacrylic acid into the system as a comonomer of cyclohexylmaleimide allows increasing the heat resistance of organic glasses.