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311.
Abstract The polymerization of vinyl monomers initiated by dimethylhydroxylamine hydrochloride (DHA)-titanous(III) chloride redox system has been studied in water under a nitrogen atmosphere. In the polymerization of methyl methyacrylate (MMA) initiated by the above system, the rate of polymerization has been found to be proportional to [DHA]0.5 for DHA concentrations of less than 2.06 × 10?3 mole/liter, whereas at higher concentrations the rate tends to fall rapidly. The rate has also been found to be proportional to [Ti(m)] 0.58 and to [MMA] 1.0. The maximum rate of polymerization has been observed at a 1:1 molar ratio of DHA to Ti(III). The polymerization proceeded via a radical mechanism. The overall activation energy was estimated as 5.5 kcal/mole. It has been suggested that the reduction of dimethylhydroxylamine by titanous(III) chloride yields the dimethylamino radical, which initiates vinyl polymerization. An examination of the initiating capacity of the initiator system for the polymerization of some vinyl monomers has also been made. 相似文献
312.
In the preceding papers of this series, we reported the synthesis of liquid-crystalline polyurethanes containing mesomorphic moieties in the main chain and in side chains [1–4]. Liquid crystalline polymers with side groups containing the cholesterol moiety have also been studied [5, 6]. The main focus of attention has centered around the study of phase transitions of acrylic and methacrylic derivatives of cholesterol. This paper describes the synthesis of a new type of liquid-crystalline polyurethane containing the cholesterol moiety in side chains. 相似文献
313.
Nakamura M Okaue T Takada T Yamana K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(1):196-201
π-Stacked naphthalenediimide (NDI) arrays are of interest as charge-transport materials. We have designed and synthesized an NDI derivative with two Zn(II)-cyclens that act as receptors for the thymine base in DNA. UV/Vis and CD spectroscopy, gel filtration, and molecular-modeling studies have shown that the bis(Zn(II)-cyclen)-NDI can be assembled in the presence of oligo-dT to form π-stacked NDI arrays. The assembly of the NDI arrays was found to be dependent on the length of the oligo-dT and the temperature. The NDI-oligo-dT assembly on a gold substrate exhibits photocurrent responses due to electron transfer through the π-stacked array. 相似文献
314.
DNA oligomers possessing a 2-nitrobenzyl (NB) protected thiol group have been prepared. The photo-remove of the NB to generate a free thiol group in DNA has been analyzed by using reverse-phase HPLC and denaturing gel electrophoresis. The photo-triggered generation of the thiol function in DNA was applicable in the light-initiated ligation of thiol-modified DNA oligomers and Au–DNA conjugation. 相似文献
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New polyurethanes ( 4a, 4b ) and a segmented polyurethane ( 4c ) bearing phosphatidylcholine moieties in the main chain were synthesized. They are thermally stable up to 300°C and show the viscosity behaviour of common polyelectrolytes. Preliminary studies suggest that these polyurethanes are interesting new biomaterials. 相似文献