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Cellulose-based macroinitiators with predetermined number of initiation sites were synthesized by acylation of microcrystalline cellulose AVICEL PH-101 with 2-bromoisobutyryl bromide under homogeneous reaction conditions in the N,N-dimethylacetamide/LiCl solvent system. The influence of different methods of cellulose activation on acylation efficiency and reproducibility was investigated. Best results were obtained using thermal activation under reduced pressure or the newly introduced protocol based on solvent exchange to 1,4-dioxane. Prepared macroinitiators were used for grafting with styrene and methyl methacrylate (MMA) using optimized atom transfer radical polymerization reaction conditions to achieve well-controlled polymerizations with high initiation efficiency. For MMA grafting, the initiation efficiency was shown to be dependent on certain reaction conditions, such as type of solvent, monomer concentration, or the presence of a sacrificial initiator. In addition, single-electron transfer liv-ing radical polymerization with Cu(0) as the catalyst was used for the first time to prepare cellulose-graft-polystyrene and cellulose-graft-poly(MMA) copolymers in a homogeneous phase. In summary, homogeneous reaction conditions, stoichiometric control in the preparation of macroinitiators, and controlled grafting jointly allowed for an extensive control of copolymers architecture, that is, density of grafting, composition, and molecular parameters of grafts. Moreover, some of the prepared copolymers were characterized by static and dynamic light scattering and microscopic techniques (transmission electron microscopy and atomic force microscopy).

ABCBA-type pentablock copolymers of methyl methacrylate (MMA), styrene (S), and isobutylene (IB) were prepared by a three-step synthesis, which included atom transfer radical polymerization (ATRP) and cationic polymerization: (1) poly-(methyl methacrylate) (PMMA) with terminal chlorine atoms was prepared by ATRP initiated with an aromatic difunctional initiator bearing two trichloromethyl groups under CuCl/2,2Ј-bipyridine catalysis; (2) PMMA with the same catalyst was used for ATRP of styrene, which produced a poly(S-b-MMA-b-S) triblock copolymer; and (3) IB was polymerized cationically in the presence of the aforementioned triblock copolymer and BCl 3 , and this produced a poly(IB-b-S-b-MMA-b-S-b-IB) pentablock copolymer. The reaction temperature, varied from Ϫ78 to Ϫ25°C, significantly affected the IB content in the product; the highest was obtained at Ϫ25°C. The formation of a pentablock copolymer with a narrow molecular weight distribution provided direct evidence of the presence of active chlorine at the ends of the poly(S-b-MMA-b-S) triblock copolymer, capable of the initiation of the cationic polymerization of IB in the presence of BCl 3 . A differential scanning calorimetry trace of the pentablock copolymer (20.1 mol % IB) showed the glass-transition temperatures of three segregated domains, that is, polyisobutylene (Ϫ87.4°C), polystyrene (95.6°C), and PMMA (103.7°C) blocks. One glass-transition temperature (104.5°C) was observed for the aforementioned triblock copolymer.

Graft copolymers with cellulose diacetate (CDA) backbone and both the poly(ε‐caprolactone) and polystyrene, or poly(butyl acrylate) or PMMA grafts were prepared by two‐step process. First, ε‐caprolactone (CL) was polymerized by ring‐opening polymerization (ROP) initiated with CDA, partly funcionalized with 2‐bromo‐isobutyryl groups (degree of functionalization was 0.5). The p(CDA‐g‐CL) copolymers were used in the second step as polyfunctional macroinitiators of ATRP of the vinyl monomer, giving densely grafted copolymers with polyester and PSt, or PBuA, or PMMA grafts. The prepared copolymers were characterized by SEC, some of them also by FTIR spectroscopy and atomic force microscopy (AFM). © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 564–573, 2008

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