The ring‐opening polymerization of ε‐caprolactone (ε‐CL) and δ‐valerolactone (δ‐VL) using nine catalytic systems consisting of a combination of three C2v zirconocene complexes and three borate cocatalysts is discussed. The polymerizations proceed in a well‐controlled manner, producing polymers with relatively high molecular weights and narrow molecular weight distributions. Kinetic experiments of the polymerization of ε‐CL with the catalytic system Cp2ZrMe2/B(C6F5)3 (1) showed a linear dependence between polymerization yield and molecular weight with time, as well as between the molecular weight with the molar ratio of the monomer over the catalyst [ε‐CL]/[Zr], indicating sufficient control of the polymerization reaction. The catalytic system (1) was utilized for the synthesis of well‐defined block copolymers of MMA with ε‐CL and δ‐VL. All samples were characterized by size exclusion chromatography, nuclear magnetic resonance, and differential scanning calorimetry. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3524–3537, 2007

Three non‐bridged dimethylzirconocene complexes; i.e., bis(η5‐cyclopentadienyl)dimethylzirconium (1), bis(η5‐tert‐butyl‐cyclopentadienyl)dimethylzirconium (2), bis(η5‐indenyl)dimethylzirconium (3), and the chiral zirconocene rac‐ethylenebis(η5‐indenyl)dimethylzirconium (4) were synthesized and used as catalysts for the polymerization of methyl methacrylate, MMA, combined with tris(pentafluorophenyl)borate (A) or tetrakis(pentafluorophenyl)borate dimethylanilinum salt (B) in the presence of ZnEt2. The evolution of the polymerization characteristics; i.e., molecular weight, molecular‐weight distribution, and yield were examined for the above systems. The influence of the nature of the solvent was also investigated. The aggregation behavior, the steric hindrance, and the lipophilicity of the active catalytic systems are the most important parameters determining the polymerization characteristics. The tacticity of the products is reported and the influence of the catalyst structure is discussed. Finally, the polymerization of other methacrylates (alkyl = butyl, hexyl, decyl, stearyl, and sec‐butyl), was conducted and the effect of the nature of the alkyl ester group on the molecular and structural characteristics was established.

Well-defined graft copolymers with poly(methyl methacrylate) backbone and poly(styrene) (PS), poly(isoprene) (PI), or poly(dimethylsiloxane) (PDMS) branches were synthesized by combining anionic and metallocene catalyzed polymerization. The synthetic strategy involves the preparation of methacryloyl macromonomers of PS, PI, and PDMS by anionic polymerization, followed by copolymerization with methyl methacrylate using the highly reactive catalytic system Cp 2ZrMe2/B(C6F5)3/ZnEt2. The macromonomers and the fractionated graft copolymers were characterized by size exclusion chromatography, low-angle laser light scattering, and 1 H NMR spectroscopy.

Polymerization of methyl methacrylate (MMA) by the three component catalytic system Cp2ZrMe2/B(C6F5)3/ZnEt2 (1), in toluene, under thoroughly purified conditions, was found to produce polymers of high molecular weights (M w > 60 × 103), low polydispersities (M w/M n = 1.12−1.22) and almost quantitative yields. The polymerization process is characterized by a pronounced induction period followed by a rapid and constant rate of polymerization. The molecular weight of PMMA increases by increasing the conversion and is proportional to the ratio of [MMA]0/[Zr]0, while M w/M n remains intact, meaning that the present polymerization proceeds in a well-controlled fashion. Evidence for effects of [ZnEt2] and temperature in the molecular characteristics of the final products are also presented in this study. Moreover, the catalytic system 1 was found to catalyze the polymerization of other alkyl methacrylates (alkyl = n-butyl, n-hexyl) to high molecular weight syndiotactic materials, with narrow molecular weight distribution, in very high conversion. Well-controlled copolymerization of MMA with n-hexyl methacrylate was successful by the effective catalytic action of 1, leading to multiblock polymeric structures. Copolymerization of MMA with stearyl methacrylate was also achieved, with the above-mentioned catalytic system. Evidence for the aggregation of the polymeric products in THF and toluene solutions was found by static and dynamic light scattering. The comparison of the polymerization results of this work with other studies clearly shows that in order to obtain improved molecular characteristics, thorough purification protocols should be applied.

Graft copolymers having poly(methyl methacrylate), PMMA, backbone and polystyrene, PS, polyisoprene, PI, poly(ethylene oxide), PEO, poly(2-methyl-1,3-pentadiene), P2MP, and PS-b-PI branches were prepared using the macromonomer methodology and high-vacuum techniques. The methacrylic macromonomers, mMM, were synthesized by anionic polymerization, whereas their homopolymerization and copolymerization with MMA were performed by metallocene catalysts. Relatively high macromonomer conversions were obtained in all cases. The parameters affecting the polymerization characteristics were examined. Well-defined poly(butyl methacrylate)-b-poly(methyl methacrylate) block copolymers were prepared for the first time by sequential addition of monomers starting from n-butyl methacrylate. The samples were characterized by size exclusion chromatography, SEC, 1 H and 13 C NMR spectroscopy, low-angle laser light scattering, LALLS, and differential scanning calorimetry, DSC.