The effects of simple alkyl alcohols on the radical polymerization of N‐isopropylacrylamide in toluene at low temperatures were investigated. We succeeded in the induction of syndiotactic specificity and the acceleration of polymerization reactions at the same time by adding simple alkyl alcohols such as 3‐methyl‐3‐pentanol (3Me3PenOH) to N‐isopropylacrylamide polymerizations. The dyad syndiotacticity increased with a decrease in the temperature and an increase in the bulkiness of the added alcohol and reached up to 71% at −60 °C in the presence of 3Me3PenOH. With the assistance of NMR analysis, it was revealed that the alcohol compounds played dual roles in this polymerization system; an alcohol compound coordinating to the NH proton induced syndiotactic specificity, and that hydrogen‐bonded to the CO oxygen accelerated the polymerization reaction. The effect of syndiotacticity on the properties of poly(N‐isopropylacrylamide)s was also examined in some detail. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4450–4460, 2006

The copolymerization of divinylbenzene (DVB) and ethylstyrene (EtSt) was carried out at 70 and 80 °C in benzene with dimethyl 2,2‐azobisisobutyrate (MAIB) at high concentrations as initiator in the presence of methyl benzyloxyiminoacetate (MBOIA), a glyoxylic oxime ether, as a retarder. The copolymerization system of DVB (0.25 mol/L), EtSt (0.25 mol/L), MBOIA (0.5 mol/L), and MAIB (0.5 mol/L) gave benzene‐soluble copolymers despite a considerably high concentration of DVB as an excellent crosslinker. The yield and molecular weight of the resulting copolymers increased with time both at 70 and 80 °C and then leveled off because of initiator consumption. The homogeneous polymerization system involved electron spin resonance (ESR), observable nitrogen‐centered polymer radicals (MBOIA·) under the actual polymerization conditions. The MBOIA· concentration increased with time despite a homogeneous polymerization system, suggesting the formation of rigid hyperbranched polymers. A benzene solution of isolated copolymer also showed an ESR signal. The copolymer was soluble in acetone, toluene, chloroform, ethyl acetate, tetrahydrofuran, and N,N‐dimethylformamide but insoluble in n‐hexane, methanol, and dimethyl sulfoxide. MAIB fragments as high as 30–40 mol % were incorporated into the copolymers through initiation and primary radical termination, on the basis of which this polymerization was named the initiator‐fragment incorporation radical polymerization. MBOIA (13–16 mol%) was also incorporated into the copolymers through an opening of the CN bond. The intrinsic viscosity of the copolymers was very low (0.08 dL/g), and the reduced viscosity was almost independent of the polymer concentration, supporting a hyperbranched structure of them. Gel permeation chromatography and multi‐angle laser light scattering and transmission electron microscopy revealed that the copolymer was formed as a hyperbranched nanoparticle. The thermal behavior of the copolymer was examined by dynamic thermogravimetry and differential scanning calorimetry. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3038–3047, 2003

The copolymerization of divinylbenzene (DVB) and N‐isopropylacrylamide (NIPAm) with dimethyl 2,2′‐azobisisobutyrate of a concentration as high as 0.50 mol/L proceeded homogeneously without any gelation at 80 °C in N,N‐dimethylformamide, where the concentrations of DVB and NIPAm were 0.15 and 0.50 mol/L. The copolymer yield increased with time and leveled off over 50 min. Although DVB was consumed more rapidly than NIPAm, both comonomers were completely consumed in 50 min. The homogeneous polymerization system at 80 °C involved electron spin resonance‐observable propagating polymer radicals, the total concentration of which increased with time. The resulting copolymer was soluble in tetrahydrofuran, chloroform, acetone, ethyl acetate, acetonitrile, N,N‐dimethylformamide, dimethyl sulfoxide, and methanol, but insoluble in benzene, n‐hexane, and water. The copolymer showed an upper critical solution temperature (50 °C on cooling) in a methanol–water [11:3 (v/v)] mixture. Dimethyl 2,2′‐azobisisobutyrate fragments as high as 37–45 mol % were incorporated as terminal groups in the copolymers through initiation and primary radical termination. The contents of DVB and NIPAm were 10–30 mol % and 30–50 mol %, respectively. The intrinsic viscosity of the copolymer was very low (0.09 dL/g) at 30 °C in tetrahydrofuran despite high weight‐average molecular weight (1.2 × l06 by multi‐angle laser light scattering). These results indicate that the copolymer was of hyperbranched structure. By transmission electron microscopy observation, the individual copolymer molecules were visualized as nanoparticle of 6–20 nm. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1609–1617, 2004

The polymerization of divinyl adipate (DVA) as an effective cross-linker with dimethyl 2,2‘-azobis(iosbutyrate) (MAIB) was performed at 70 and 80 °C in benzene. When the MAIB concentrations as high as 0.05−0.50 mol/L were used, the polymerization of DVA (0.30 mol/L) proceeded homogeneously at 80 °C without any gelation to give soluble polymers in the yields of 45−87%. Kinetic investigation on the homogeneous polymerization at 70 °C gave the following rate equation:  R p = k[MAIB]0.3[DVA]1.7 (R p = initial polymerization rate), indicating a significant contribution of the primary radical termination. The overall activation energy of the polymerization was estimated to be 26.8 kcal/mol. The polymer formed in the polymerization of DVA (0.30 mol/L) with MAIB (0.50 mol/L) at 80 °C for 4 h was composed of the DVA units without (48 mol %) and with (8 mol %) double bond and the methoxycarbonylpropyl group (44 mol %) from MAIB. The large fraction of the incorporated initiator-fragment implies that an initiator-fragment incorporation polymerization proceeded to give hyperbranched polymer in the present polymerization. The results of the multiangle laser light scattering and viscometric measurements and also transmission electron microscopic observation indicate that the polymer was of compact hyperbranched structure. The polymer showed an upper critical solution temperature (36 °C on cooling) in an acetone−water [7:40 (v/v)] mixture and also exhibited the encapsulation and transport properties for Rhodamine 6G as a dye probe.

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The radical polymerizations of N‐isopropylacrylamide (NIPAAm) were carried out in toluene at low temperatures in the presence of phosphoric acid esters such as trimethyl phosphate, triethyl phosphate (TEP), tri‐n‐propyl phosphate, and tri‐n‐butyl phosphate (TBP). Syndiotactically rich poly(NIPAAm)s were obtained from −60 to 0 °C, and TEP provided the highest syndiotacticity (racemo dyad = 65%) at −40 °C. On the other hand, lowering the temperature reversed the stereoselectivity of the propagation reaction so that isotactically rich poly(NIPAAm)s were obtained at −80 °C. In particular, TBP exhibited the most isotactic specificity (meso dyad = 57%). Job's plots for NIPAAm–TBP mixtures revealed that NIPAAm and TBP formed a 1:1 complex at 0 °C and a predominantly 1:2 complex at −80 °C through a hydrogen‐bonding interaction. Therefore, the stereospecificity of NIPAAm polymerization should depend on the stoichiometry of the hydrogen‐bond‐assisted complex. Thus, the mechanism for this polymerization system was discussed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 50–62, 2005

Polymerization of dialkyl itaconates with dimethyl azoisobutyrate (5) was studied in benzene at 50 "C by means of electron spin resonance (ESR). The monomers used are dimethyl (l), diethyl (2), dibutyl (3) and di-2-ethylhexyl (4) itaconates. All the polymerization systems involve ESRobservable propagating polymer radicals under the actual polymerization conditions. The polymerization rate (R,) and degree of polymerization of the resulting polymer increase in going from shorter to longer alkyl groups. The ESR-determined rate constants of propagation (k,) and termination (k,) decrease as the alkyl chain becomes longer. k, of 1 is 3,3 times higher than that of 4, while k, of 1 is 590 times higher than that of 4. Thus, the steric effect due to the alkyl group suppresses much more termination than propagation, leading to the fact that R, increases as the alkyl group becomes larger.

The copolymerization of divinyl adipate (DVA) with isobutyl vinyl ether (IBVE) was conducted at 70 and 80 °C in benzene using azobisisobutyronitrile (AIBN), at a concentration as high as 0.50 mol l−1 as the initiator, where the concentrations of DVA and IBVE were 0.40 and 0.60 mol l−1, respectively. The copolymerization proceeded homogeneously, without any gelation, to yield soluble copolymers in spite of the high molar ratio of DVA as an excellent cross‐linker for IBVE. The copolymer yield increased with time, and the number‐average molecular weight (Mn = 0.9–2.4 × 104 g mol−1) from gel permeation chromatography (GPC) and molecular weight distribution (Mw/Mn = 1.5–7.6) of the resulting copolymer increased with copolymer yield. The cyanopropyl group, as a fragment of AIBN, was incorporated as a main constituent in the copolymer, the fraction of which increased from ca 10 to ca 20 % with copolymer yield, hence indicating that the copolymerization is an initiator–fragment incorporation radical polymerization. The copolymers also contained IBVE units (10–30 %) and DVA units with intact double bond (8–36 %) and without double bond (45 %). The intrinsic viscosity of the copolymer was very low (0.1 dl g−1) at 30 °C in tetrahydrofuran. The results from GPC–multi‐angle laser light scattering (MALLS), transmission electron microscopy (TEM) and MALLS revealed that individual copolymer molecules were formed as hyperbranched nanoparticles. Copyright © 2004 Society of Chemical Industry