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Tanaka, Kenya; Matyjaszewski, Krzysztof
doi: 10.1002/masy.200850101pmid: N/A
Summary: Controlled copolymerization of polar (meth)acrylates with non‐polar olefin monomers (1‐octene, norbornene, vinylcyclohexane) was studied by ARGET (activators regenerated by electron transfer) ATRP (atom transfer radical polymerization). When a normal ATRP of n‐butyl acrylate (nBA) and 1‐octene was conducted, the polymerization resulted in relatively low conversion, limited control over the polymerization process and high polydispersity (PDI > 1.6). This was due to formation of a dormant species, by reaction of 1‐octene radicals with Cu(II) deactivator, that could not be reactivated. However, in ARGET ATRP with 10 ppm amounts of Cu‐based catalyst, higher yields and a better controlled copolymerization was obtained (PDI < 1.4), because the low concentration of Cu(II) deactivator reduced the formation of the non‐reactive dormant species. The influence of the amount of Cu catalyst, ligand structure, initiators with different halogens, the reaction temperature, and monomer feed ratio were also investigated for ARGET ATRP. In copolymerization of (meth)acrylates with non‐polar alkenes, the level of control and the total conversion in ARGET ATRP were higher than those for normal ATRP.
Scharlach, Katrin; Kaminsky, Walter
doi: 10.1002/masy.200850102pmid: N/A
Summary: Polypropylene‐nanocomposites were prepared by in‐situ polymerization with the catalysts systems rac[Et(IndH4)2]ZrCl2, Me2Si(Flu)(Ind)ZrCl2 and rac[Me2Si(2‐Me‐4‐(1‐Naph)Ind)2]ZrCl2. The type and size of the nanoparticles and the concentration of the propene were varied. The activity is independent of the type and the size of the filler. It was observed that the filler contents in the polypropylene‐nanocomposites depend on the catalysts system used. The morphology results using TEM revealed that the nanoparticles are uniformly distributed in the isotactic polypropylene matrix. Additionally, the melting points, glass temperatures and crystallization temperatures changed with the amount of the fillers.
Goto, Atsushi; Hirai, Norihiro; Tsujii, Yoshinobu; Fukuda, Takeshi
doi: 10.1002/masy.200850103pmid: N/A
Summary: Phosphorus compounds were employed as catalysts in Reversible Chain Transfer Catalyzed Polymerization (RTCP), a novel class of living radical polymerization (LRP) which we had recently developed. Low‐polydispersity polystyrene and poly(methyl methacrylate) with predicted molecular weights were obtained with a fairly high conversion in a fairly short time. These catalysts are particularly featured by their high reactivity hence small amounts being required, low toxicity, and low cost. Some phosphorus catalysts used in this work are among the least expensive catalysts/mediators of LRP developed so far.
Zhang, Wei; Wang, Chengchao; Li, Daoguang; Song, Qing; Cheng, Zhenping; Zhu, Xiulin
doi: 10.1002/masy.200850104pmid: N/A
Summary: Two multifunctional iniferters, 1,4‐bis‐(α‐N,N‐diethyldithiocarbamyl‐isobutyryloxy)‐benzene (BDCIB) and 1,3,5‐tris‐(α‐N,N‐diethyldithiocarbamyl‐isobutyryloxy)‐benzene (TDCIB), were successfully synthesized and used as initiators to initiate the polymerization of styrene in the presence of a CuBr/PMDETA complex. The polymerization results demonstrated that the kinetic plots in all cases were first‐order to the monomer, the molecular weight of the polymers increased linearly with the monomer conversion; meanwhile, the molecular weight distribution of the polymer was kept to a very low value (Mw/Mn ≤ 1.35). Furthermore, the measured molecular weights were very close to the calculated values, which indicated the high efficiency of the initiator for the polymerization of styrene. The effect of catalyst concentration and initiator concentration was not obvious and the influence of polymerization temperature was apparent, and the polymerization rate increased with the polymerization temperature. The results of chain‐extension and 1H NMR analysis proved that the polymer obtained was capped with diethylthiocarbamoylthiy (DC) group.
Simms, Ryan W.; Cunningham, Michael F.
doi: 10.1002/masy.200850105pmid: N/A
Summary: The reverse atom transfer radical polymerization of butyl methacrylate in miniemulsion, initiated with the redox pair hydrogen peroxide/ascorbic acid and mediated with copper(II) bromide tris[2‐di(2‐ethylhexyl acrylate)aminoethyl]amine is capable of producing well‐controlled high‐molecular weight poly(butyl methacrylate).
doi: 10.1002/masy.200850106pmid: N/A
Summary: For the controlled/living radical polymerization (CLRP) in which the active period during the chain formation is extremely small, ϕA < 1, such as the cases of usual SFRP and ATRP, the polymerization rate can be made larger by increasing the average number of monomeric units added during a single active period, $\bar P_{n,SA}$. The $\bar P_{n,SA}$‐value is inversely proportional to the trapping agent concentration [X], and the polymerization rate is controlled by [X]. For small particles, even with a single trapping agent, [X] in the particle could be larger than that in corresponding bulk polymerization, and the polymerization rate decreases with D p3, where Dp is the particle diameter. On the other hand, for CLRPs whose ϕA‐value is not very much smaller than unity, say ϕA>0.01, such as some of RAFT polymerization systems, the polymerization rate can be made larger by increasing the kinetic chain length for a given initiation frequency. For such reaction systems, the polymerization rate can be enhanced significantly by employing the emulsified polymerization systems.
Zhu, Jian; Zhu, Xiulin; Cheng, Zhenping; Zhang, Zhengbiao
doi: 10.1002/masy.200850107pmid: N/A
Summary: The reversible addition–fragmentation chain transfer (RAFT) random copolymerization of N‐vinylcarbazole (NVC) and vinyl acetate (VAc) was carried out using s‐benzyl‐o‐ethyl dithiocarbonate (BED) as the chain transfer agent and 2,2′‐azoisobutyronitrile (AIBN) as the initiator in 1,4‐dioxane solution at 70 °C. The polymerization showed the characteristics of ‘living’ free radical polymerization behaviors: first order kinetics, linear relationships between molecular weight and conversion, and narrow polydispersity of the polymers. The reactivity ratios of NVC and VAc were calculated via the Kelen–Tudos (KT) and non‐linear error in variable (EVM) methods and showed as r1 = 1.938 ± 0.191, r2 = 0.116 ± 0.106. The thermal behavior of the copolymers with different content of NVC and VAc was investigated by DSC and TGA. The results showed that the introduction of a VAc segment into copolymer significantly reduced the Tg of the NVC homopolymers. FT‐IR spectra, fluorescence spectra, and cyclic voltammetric behavior of these copolymers were also measured and compared with those of NVC homopolymers. The copolymers showed similar oxidative behavior to the NVC homopolymer. However, there was only one reductive potential peak shown for the copolymers at about 0.058 V.
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