Polymerization Of Methyl Methacrylate In Toluene Research Articles

Sulfur-Free Radical RAFT Polymerization of Methacrylates in Homogeneous Solution: Design of exo-Olefin Chain-Transfer Agents (R-CH2 C(=CH2 )Z).

In this work, the development of exo-olefin compounds (R-CH2 C(=CH2 )Z) as chain-transfer agents for the sulfur-free reversible addition-fragmentation chain transfer (RAFT) radical polymerization of methacrylates in homogeneous solution is described. A series of exo-olefin compounds with a methyl methacrylate (MMA) dimer structure as the R group and a substituted α-methylstyrene unit as the -CH2 C(=CH2 )Z (Z: Ph-Y) group were synthesized and used for the radical polymerization of MMA in toluene and PhC(CF3 )2 OH. These compounds underwent transfer of the CH2 C(=CH2 )Z group via addition-fragmentation of the propagating methacryloyl radical. More electron-donating (Y) substituents, such as methoxy and dimethylamino groups, produced polymers with narrower molecular weight distributions. A continuous monomer addition method further improved molecular weight control and enabled the synthesis of colorless, sulfur-free, multiblock copolymers of methacrylates in homogeneous solutions.

Sulfur‐Free Radical RAFT Polymerization of Methacrylates in Homogeneous Solution: Design of exo‐Olefin Chain‐Transfer Agents (R−CH2C(=CH2)Z)

AbstractIn this work, the development of exo‐olefin compounds (R−CH2C(=CH2)Z) as chain‐transfer agents for the sulfur‐free reversible addition‐fragmentation chain transfer (RAFT) radical polymerization of methacrylates in homogeneous solution is described. A series of exo‐olefin compounds with a methyl methacrylate (MMA) dimer structure as the R group and a substituted α‐methylstyrene unit as the −CH2C(=CH2)Z (Z: Ph−Y) group were synthesized and used for the radical polymerization of MMA in toluene and PhC(CF3)2OH. These compounds underwent transfer of the CH2C(=CH2)Z group via addition‐fragmentation of the propagating methacryloyl radical. More electron‐donating (Y) substituents, such as methoxy and dimethylamino groups, produced polymers with narrower molecular weight distributions. A continuous monomer addition method further improved molecular weight control and enabled the synthesis of colorless, sulfur‐free, multiblock copolymers of methacrylates in homogeneous solutions.

Polymerization of methyl methacrylate by latent pre-catalysts based on CO2-protected N-heterocyclic carbenes

Various carbon dioxide-protected N-heterocyclic carbenes (NHCs) have been investigated with regard to their ability to act as thermally latent initiators for the polymerization of methyl methacrylate (MMA). Such CO2-protected NHCs, while completely inactive at room temperature, deliver poly(methyl methacrylate) (PMMA) in high yields upon heating and thus represent truly latent pre-catalysts. Polymerizations were conducted in the bulk, semi-bulk and in solution. Especially tetrahydropyrimidinium-2-carboxylates as well as 1,3-di(tert-butyl)imidazolium-2-carboxylate, both in combination with dimethylsulfoxide (DMSO), were identified as suitable pre-catalysts for the polymerization of MMA. With 1,3-di(tert-butyl)imidazolium-2-carboxylate in toluene, polydispersity indices (PDIs) as low as 1.3 and number-average molecular weights (Mn) of 500 000 g mol−1 could be realized. Tetrahydropyrimidinium-2-carboxylates in conjunction with DMSO resulted in lower molecular weights. Notably, isolated polymer yields up to 96% were possible in some cases, though yields proved to be sensitive to the structure of the initiators used. In principle, at least two different polymerization mechanisms are active. In the presence of DMF or DMSO, the formation of a solvent anion (e.g., DMSO−), which then reacts with the monomer, is proposed. What follows is that only highly basic NHCs work well under these conditions. In contrast, the polymerization of MMA in toluene or in the bulk is probably governed by the nucleophilicity of the NHC, rendering unsaturated, less basic NHCs more applicable. Both mechanisms are discussed.

Macrothiuram disulfide for the free radical synthesis of PDMS‐vinyl triblock copolymers. II. Studies of chain transfer

AbstractChain transfer constants (Ctr) for thiuram disulfide (TD) groups, included in the backbone of polydimethylsiloxane (PDMS) of different chain lengths, in methyl methacrylate (MMA) and styrene (St) were determined from measurements of the degree of polymerization. Two methods were used. The first consisted of using the initiation and transfer properties of the thiuram disulfides groups, and the second, of using a more efficient free radical initiator than TD groups, in which case the former behaves only as a transfer agent. In both the methods, the Ctr of TD was evaluated in bulk polymerization of MMA at 60, 70, 80, and 90°C. Using the first method, the Ctr of TD was measured also in solution polymerization of MMA in toluene at 100°C and, with the second one, in bulk polymerization of styrene at 60, 80, and 90°C. PDMS‐based macrothiuram disulfide (macroiniferter) behaves as an “azeotropic” transfer agent for MMA and styrene at 125°C and 110°C, respectively. © 1994 John Wiley & Sons, Inc.