Marina Fernández-Sanz

The importance of solvent polar character on the synthesis of PMMA-b-PBA block copolymers by atom transfer radical polymerization

Abstract The synthesis of diblock copolymers using atom transfer radical polymerization (ATRP), of methyl methacrylate (MMA), and butyl acrylate (BA), is reported. These copolymers were prepared from bromo-terminated macroinitiators of poly(MMA) and poly(BA), using copper chloride, CuCl,/N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA), as catalyst system, at 100°C in bulk and in benzonitrile solution. The block copolymers were characterized by means of size exclusion chromatography (SEC), and 1H-NMR spectroscopy. The SEC analysis of the synthesized diblock copolymers confirmed the importance of solvent on the molecular weight control. In addition, differential scanning calorimetry (DSC), measurements were performed, showing for all the copolymers a phase separation.

Solvent effects on the synthesis of poly(methyl methacrylate) by atom-transfer radical polymerization (ATRP)

Methyl methacrylate has been polymerized by ATRP at 100°C in bulk, in toluene (50%, v/v) and benzonitrile (50% and 25%, v/v), using methyl 2-halopropionate as initiator (MeXPr, X = Cl or Br), copper halide (CuX) as catalyst and 2,2′-bipyridine (bpy) as ligand. The mixed halogen system MeBrPr/CuCl has also been used. For all initiator systems used, the bulk polymerizations showed linear first-order rate plots, a linear increase of the number-average molecular weight with conversion, and relatively low polydispersities, but low initiator efficiency. The polymerizations performed in toluene do not significantly increase the polymerization efficiency, but the molecular weight distribution is broadened. When the polymerizations are performed in benzonitrile, the polymerization efficiency increases considerably, but is independent of monomer dilution. The molecular weight distributions are narrowed when the polymerizations are performed in 25% (v/v) benzonitrile solution. Experimental number-average molecular weights match the theoretical values when the polymerizations are carried out using the mixed halogen initiator system in benzonitrile solution.

A Comparative Study of Methyl Methacrylate/Butyl Acrylate Copolymerization Kinetics by Atom‐Transfer and Conventional Radical Polymerization

Methyl methacrylate and butyl acrylate monomers are copolymerized by atom-transfer radical polymerization, affording polymers with well-controlled molecular weight and low polydispersity. A kinetic analysis of this system is compared with the corresponding free-radical polymerization system. The copolymerization rate follows an opposite trend to that observed in conventional copolymerization. This fact is attributed to a smaller population of radicals generated in the reaction, since the relative fraction of propagating radicals is the same as that in classical copolymerization.

Solvent effects on the free-radical copolymerization of styrene with butyl acrylate. I. Monomer reactivity ratios

The free-radical copolymerization of styrene with butyl acrylate was carried out in benzene and benzonitrile at 50°C. Differences between the apparent reactivity ratios determined in this work and those previously reported in bulk indicated noticeable solvent effects. This is explained by a qualitative bootstrap effect.

An Analysis of the Solvent Effects on the Monomer Reactivity Ratios Using the Copolymer Glass Transition Temperatures

The glass transition temperatures (T g ) of styrene-butyl acrylate copolymers obtained by free radical polymerization in bulk, and in 3 mol.L -1 benzene and benzonitrile solutions, have been measured using differential scanning calorimetry (DSC) to verify the boot-strap effect previously reported for this system. The corresponding values have been correlated with copolymer composition and microstructure using the Johnston equation.

Glass Transition Temperatures of Poly[(methyl methacrylate)-co-(butyl acrylate)]s Synthesized by Atom-Transfer Radical Polymerization

Glass transition temperatures Tg of methyl methacrylate/butyl acrylate copolymers obtained by means of atom-transfer radical polymerization are measured using differential scanning calorimetry. Due the nature of this polymerization method an increase in molecular weight is produced as the reaction progresses, which gives rise to an increase in Tg. Simultaneously, a composition gradient with the enrichment of butyl acrylate causes a decrease in Tg. These opposite effects almost compensate each other and, therefore, no influence on the molecular weight at Mn < 10000 is found. This fact allows the application of the Johnstons equation and the Mayo-Lewis terminal model to describe and predict the variation in Tg with copolymer conversion for the copolymers and under the experimental conditions investigated.

A kinetic study of free radical copolymerization of styrene/butyl acrylate

The free radical copolymerization at 50°C of styrene with butyl acrylate was carried out in bulk. Although the copolymer composition is well described by the Mayo-Lewis terminal model, the copolymerization rate is not. As many other systems rcccntly examined, the data are well represented by the implicit penultimate effect model. Values of monomer and radical reactivity ratios are qualitatively rationalized in terms of the enthalpic and entropic models.