Azo polymers — syntheses and reactions

Summary Polycarbonates containing different amounts of thermolabile azo functions have been synthesized. The resulting polymeric initiators have been used to start the polymerization of methyl methacrylate. The kinetic results are explained on the basis of a high degree of termination reactions by primary radicals.     

Azo polymers — syntheses and reactions

Summary Azo group containing polycarbonates were used as initiators for the polymerization of methyl methacrylate. The grafting reaction was characterized by the terms: grafting success U_g, grafting efficiency and degree of grafting . The effect of the monomer and initiator concentration on these terms is discussed in detail. The number of grafted sidearms is determined by complete hydrolysis of the polycarbonate backbone.     

Degradative reactions of decadienoate esters

Methyl and ethyl esters of decadienoic acid, which are normal constituents of the Bartlett pear, react with oxygen in the presence of light to produce n-hexanal, and the methyl or ethyl 4-oxybutenoate. The products were separated by gas chromatography, and identified by melting points, infrared spectroscopy, and/or the formation of derivatives. Possible reaction mechanisms are discussed. Parts of this paper are from a thesis submitted by D. E. Heinz in partial satisfaction of the requirements for the PhD degree in Agricultural Chemistry.     

Degradative addition reactions in relation to protein-bound cystine

A study has been made of the degradation of protein-bound cystine, in various proteins, when degraded by alkali in the presence of aliphatic amines. This shows that the structure of amine has a significant effect on the rate of degradation of the cystine. The products of degradation of cystine which resulted from the intermediate, dehydroalanine, have been determined quantitatively at different temperatures of treatment. Attempts are made to correlate the amounts of products with the nature of the amines used and the hydrophobicity of the proteins.     

Transesterification reactions in molten polymers

The transesterification reaction of molten ethylene and vinyl alcohol copolymers (EVA), in presence of paraffinic alcohols and basic catalysts, leads to high conversion of the ester groups to secondary alcohol in both discontinuous and continuous processing equipment. Various kinds of alcohols and two different catalysts were used. Sodium methoxide is a powerful catalyst for the equilibrated transesterification reaction, but we also observed side reactions, such as cross-linking with low-molecular-weight alcohols and hydrolysis of the catalyst followed by partial saponification of the EVA. Kinetic studies were performed in the presence of dibutyltin dilaurate, an efficient catalyst without any side reactions. The solubility of the main alcohol reagents was verified by diffusion measurements. The general reaction scheme and the related kinetics, corresponding to a homogeneous system, lead to a fair evaluation of the rate constants.     

电化学合成含交替苯/噻吩结构的电致变色聚合物

利用Kumada偶联合成了2,5-二苯基噻吩（DPT）、1,4-二噻吩基苯（DTP）及1,4-二（3-甲基-2-噻吩基）苯（DMTP）,并电聚合得到相应的聚合物PDPT、PDTP和PDMTP。PDPT的电化学稳定性较差,而PDTP和PDMTP在0～1.2 V间具有良好的电活性。此外,PDTP和PDMTP分别具有青-橙和红-绿-蓝的电致变色现象,可用于电致变色器件。     

Metal-directed syntheses of coordination polymers via in situ ligand reactions from the same precursor, 2-(1H-benzeimidazol-2-yl)-acetonitrile

Three new coordination polymers, [Co(HBit)₂]_n (1), [Mn(HBit)₂]_n (2) (H₂Bit = 2-((1H-tetrazol-5-yl)methyl)-1H-benzo[d]imidazole), and [CdCl(MBi)(HMBi)]_n (3), (HMBi = 2-methyl-1H-benzo-[d]imidazole), have been hydrothermally synthesized via in situ ligand reaction. Compounds 1 and 2 are isomorphous and display interesting 3D chiral supramolecular frameworks constructed from one-dimensional 4₁ helical chains. Complex 3 possesses a one-dimensional coordination chain, which is further connected to a 2D layer by intermolecular hydrogen bonds. More interestingly, both H₂Bit and HMBi ligands are in situ generated from the same precursor, 2-(1H-benzo[d]imidazol-2-yl)-acetonitrile, and the formation may depend on the kind of metal ion. Furthermore, the solid-state luminescence of complex 3 was investigated at room temperature.     

The importance of char-forming reactions in thermoplastic polymers

The flammability and smoke generated from burning blends of acrylonitrile–butadiene–styrene (ABS) and polyvinylchloride (PVC) are discussed. Flammability was measured using standard oxygen index techniques and smoke production determined by the NBS method. The incorporation of some specific iron containing inorganic compounds into a range of blends of ABS and PVC considerably changes the burning characteristics of the polymer blend. Thermal stability at elevated temperatures and carbonaceous char formation are also discussed. The chemical role of iron compounds in reducing both the flammability and smoke production in ABS/PVC is considered.     

Paramagnetic conjugated polymers with stable radicals in side groups

Summary Poly(1,3-dihydroxy-2-(4-ethynylphenyl)-4,4,5,5-tetramethylimidazolidine), poly(2-(4-ethynylphenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxyl-3-oxide), poly(4-(4-ethynylbenzylideneamino)-2,2,6,6-tetramethylpiperidine) and poly(4-(4-ethynylbenzylideneamino)-2,2,6,6-tetramethylpiperidine-1-oxyl) were prepared from poly(4-ethynyl-benzaldehyde). The products were characterized spectroscopically (IR, UV, ¹H and ¹³C NMR) and with respect to the magnetic susceptibility. The polyradicals (1-oxyl compounds) showed paramagnetic properties obeying Curie's law.     

Photo-crosslinkable polymers with benzylideneacetophenone (chalkone) structure in the side chains

Four soluble types of polymers have been synthesized by grafting 4- and 4′-chalkonyl glycidyl ethers onto an aromatic polyamine (aniline–formaldehyde linear resin) and a polyamide (condensation product of dimerized linseed oil and an aliphatic polyamine) to obtain photo-crosslinkable chalkone structure in the side chains which are also expected to contain one ? OH group each. The completion of grafting reactions has been followed by the disappearance of the epoxide absorption around 918 cm^?1. The characterization of the resins was done by melting point, solubility, and IR measurements. Irradiation was carried out with a 100-watt Hanovia high-pressure mercury are lamp. Irradiated samples were studied by UV spectral measurements and their insolubility in CHCl₃. It was observed that polymers grafted with 4′-chalkonyl glycidyl ether possibly undergo both isomerization and crosslinking reactions under UV irradiation while those grafted with 4-chalkonyl glycidyl ether undergo crosslinking reaction predominantly.     

Europium‐containing cholesteric liquid crystalline polymers in the side chain

Europium‐containing cholesteric liquid crystalline polymers were graft copolymerized using poly(methylhydrogeno)siloxane, cholesteryl 4‐(allyloxy)benzoate (M₁), cholesteryl acrylate (M₂), and a europium complexes monomer (M₃). The chemical structures of the monomers were characterized by Fourier transform infrared and ¹H‐nuclear magnetic resonance. The mesomorphic properties and phase behavior were investigated by differential scanning calorimetry, thermo gravimetric analysis, polarizing optical microscopy, and X‐ray diffraction. With an increase of europium complexes units in the polymers, the glass transition temperature (T_g) did not change significantly; the isotropic temperature (T_i) and mesophase temperature range (ΔT) decreased. All polymers showed typical cholesteric Grandjean textures, which was confirmed by X‐ray diffraction. The temperatures at which 5% weight loss occurred (T_d) were greater than 300°C for the polymers. The introduction of europium complexes units did not change the liquid crystalline state of polymer systems; on the contrary, the polymers were enabled with the significant luminescent properties. With Eu³⁺ ion contents ranging between 0 and 1.5 mol %, luminescent intensity of polymers gradually increased and luminescent lifetimes were longer than 0.45 ms for the polymers. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40866.     

Photochemical reactions of polymers bearing chalcone residues

Photosensitive polymers based on pendent chalcone moieties were prepared directly by radical polymerization of vinyl-chalcone monomers. The monomers were synthesized by the esterification reactions of the hydroxyl groups of 4- and 4′-hydroxychalcones with methacryloyl chloride. The monomers (4- and 4′-(methacryloyloxy)chalcones) were polymerized to give the corresponding homo-and co-polymers containing different ratios of p-nitrophenyl methacrylate as photosensitizer group. Investigation of the photosensitivities of the chalcone polymers was carried out through study of the photochemical reactions on exposure to UV light and measuring the changes in UV spectra before and after irradiation. The results obtained from the disappearance rates of the C=C bonds indicate that the photoreactivities of the polymers are largely affected by the position of the attachment of the chalcone to the polymer backbone and by the concentration of the photosensitizer group.     

Synthesis and characterization of bulky side chain methacrylate polymers

The synthesis, and dilute solution behavior of poly(2,4-dimethylphenyl methacrylate) (2,4DMP), poly(2,5-dimethylphenyl methacrylate) (2,5DMP), and poly(3,5-dimethylphenyl methacrylate) (3,5DMP) is described. Comparison is made with results reported for other bulky side chain polymers. The Kuhn-Mark-Houwink-Sakurada (KMHS) relationships were established. The unperturbed dimensions 〈r²〉 ${}_{\text{½}}^{\text{0}}$ , the rigidity factor σ, the characteristic ratio C_∞, and the thermodynamic parameters were determined, using the Stockmayer-Fixman equation, from viscometric data in good solvents. The high rigidity observed for these polymers is explained assuming that these polymers behave as kinked-chains.     

Synthesis of potentially piezoelectric polymers containing tetracyanocyclobutyl side groups

Three new monomers containing the tetracyanocyclobutyl substituents were synthesized: p-(tetracyanocyclobutyl) styrene 1, p-(1′-methyl-2′,2′,3′,3′-tetracyanocyclobutyl)-α-methylstyrene 2 and [p-(tetracyanocyclobutyl)phenyl] acrylate 3, with the aim of obtaining potentially piezoelectric polymers which contain substituents with high dipole moments. Moderate molecular weight polymers were obtained from monomer 1 only, 2 and 3 did not polymerize. The inhibiting effect of the tetracyanocyclobutyl group was responsible for the molecular weights as demonstrated by model experiments.     

Infrared-spectroscopic investigations of molecular order in liquid crystalline side chain polymers

Summary Infrared dichroism was used to determine the order parameters of liquid crystalline side chain polymers. By this the order parameters of the main chain, of the spacer and of the mesogenic group can be obtained separately. Therefore spectra of two liquid crystalline polyacrylates were recorded with polarized light at different temperatures. In a poly(acrylate) with 6 CH₂ groups in the spacer a high order parameter was found not only for the mesogenic group, but also for the spacer and the main chain. The orientation of the poly(acrylate) with a spacer of only 2 CH₂ groups is lower due to the stronger interaction of main chain and mesogenic group.     

Synthesis and properties of dimesogenic liquid crystalline side group polymers

Summary Liquid crystalline polymalonates with side groups consisting of two different mesogenic units separated by alkylene spacers from each other and from the polyester backbone have been prepared. According to microscopic observations, DSC measurements and X-ray studies, all polymers display smectic phases.     

Corona poling of liquid crystalline polymers with nitroazobenzene side chains

Summary The orientational behavior of liquid crystalline polymers with para-nitro azobenzene as side chains under electric field was studied by UV-visible spectroscopy. The results showed that λ_max of the poled polymer films was around 394nm, compared to that of the unpoled films, the absorption decreased due to poling. The orientational parameters increased linearly with the increase of the electric field. The temporal stability of the poled polymer film is good at room temperature. This kind of materials showed promise application as nonlinear optical component in photorefractive polymers Received: 29 January 1999/Revised version: 19 April 1999/Accepted: 21 April 1999     

Extent of side reactions and gelation of polyether polyurethanes

Summary Gelation and gel build-up due to a side reaction in poly-(oxypropylene) diol — 4,4-diisocyanatodiphenylmethane systems, catalyzed by dibutyltin dilaurate and containing excess NCO groups was studied at 60 to 140°C. Formation of allophanate groups from urethane and urea and biuret from traces of water were the main side reactions. The extent of these reactions was monitored by the determination of isocyanate reacted in excess to that consumed for the formation of urethane and urea groups. Two gel point were observed: one corresponding to the solgel transition at a low excess of NCO groups and the other one corresponding to the gelsol transition at a high excess of NCO groups. The width of the gel and the maximum amount of gel decrease with increasing temperature.     

哒螨灵在茶叶中残留量的研究

从１９９３－１９９４年哒螨灵残留量降解的研究表明，哒螨灵农药在正常用量下喷药后３天成茶中留理平均低于１．００ｐｐｍ，５天成茶中残留量平均低于０．５ｐｐｍ。饮茶过程中哒螨灵浸出率较低，平均为６．８６％，对人体是安全的。