The synthesis of second‐generation (G‐2) dendritic polymers of isoprene (I) and styrene (S) was achieved with anionic polymerization high‐vacuum techniques and by performing the following steps: (1) selective reaction of a living chain with the chlorosilane group of 4‐(chlorodimethylsilyl)styrene (a dual‐functionality compound) to produce a macromonomer, (2) addition of a second living chain (same or different) to the double bond of the macromonomer, (3) polymerization of I with the anionic sites, and (4) reaction of the produced off‐center living species with trichloromethyl silane or tetrachlorosilane (CH3SiCl3 or SiCl4). The combined characterization results showed that the G‐2 dendritic macromolecules synthesized—(S2I)3, (SI′I)3, (I″I′I)3, (I′2I)4—have a high molecular and compositional homogeneity. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1519–1526, 2002

Introduction. Polymacromonomers 1-3 are comblike polymers with an extremely high-density branching, since each monomeric unit bears a polymeric chain. Depending on the degree of polymerization of the side and the main chain, they can form either starlike or brushlike (molecular brushes) structures. The most popular polymerization of macromonomers 4-6 is by using radical initiators. [7][8][9][10] Ring-opening (ROMP), 11,12 atom transfer radical (ATRP), [13][14][15][16][17] and Ziegler-Natta 18 polymerization of macromonomers 19 have also been reported in the literature. A few attempts have been undertaken for the anionic polymerization of macromonomers without complete success. 20 It seems that during the polymerization the growing macroanions are terminated by impurities accompanying the macromonomers. These impurities are introduced during the isolation step of macromonomer by pouring the macromonomer solution into the nonsolvent. Since macromonomers are solid materials, their purification to the standards required for anionic polymerization is extremely difficult.In this communication, we are proposing a new methodology to overcome this problem by synthesizing and polymerizing the macromonomer in the same reactor and by using high-vacuum techniques.Experimental Section. Purification of all monomers (isoprene, butadiene, styrene), solvents (benzene and tetrahydrofuran), and terminating agent (methanol) were performed using standard high-vacuum techniques, described in detail elsewhere. 21 sec-Butyllithium (sec-BuLi), prepared from sec-butyl chloride and lithium dispersion, was the initiator for all polymerizations. Magnesium turnings (Aldrich) were washed with THF and dried in the vacuum line. p-Chlorostyrene was distilled under vacuum, over calcium hydride, to ampules equipped with break-seals. 4-(Chlorodimethylsilyl)styrene (CDMSS) was prepared from the Grignard reagent of p-chlorostyrene and dichlorodimethylsilane, using high-vacuum techniques, as reported in detail recently. 22 Polymerizations and linking reactions were carried out in evacuated, n-BuLi-washed, and solvent-rinsed glass reactors. Reagents were introduced via breakseals, and aliquots for characterization were removed by heat-sealing of constrictions. Full details of the highvacuum techniques are given elsewhere. 21 The apparatus of Figure 1 was used for the synthesis and polymerization of macromonomers.

Bulk free-radical polymerization of 2-vinylpyridine (2VP) in the presence of 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) was studied under different conditions (temperature and presence of additives). Linear poly-(2-vinylpyridine) with a narrow molecular weight distribution and controllable molecular weight was prepared in the presence of acetic anhydride at 95°C up to a conversion of 66%. At higher conversions side reactions became very important (pseudoliving polymerization). By applying this procedure, well-defined random copolymers of 2VP with styrene or tert-butylmethacrylate as well as block copolymers of 2VP with styrene were synthesized.

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