Comparative Studies on Properties of Polymers with Bulky Side Groups Synthesized by Cyclopolymerization of α,ω-Dienes and α,ω-Diynes

Four polymers containing five-membered rings in the main chain, with or without conjugation structure along the backbone and with or without conjugated pendent groups, were designed and synthesized by metathesis cyclopolymerization of functionalized α,ω-diynes, and cyclopolymerization of functionalized α,ω-dienes catalyzed by the α-diimine palladium-based catalyst, respectively. High to moderate monomer conversions were achieved. Chain structure, molecular weight, and molecular weight distribution(MWD) of the cyclopolymerization products were characterized by ~1 H-, ^(13) C-NMR, FTIR, and GPC. The polymers showed regular main chain structures,moderately high molecular weight, and narrow MWD. Thermal properties and chain stacking behaviors of the polymers were investigated by differential scanning calorimetry(DSC) and X-ray diffraction(XRD) as well as atomic force microscopy(AFM). The polymer with conjugation system in both the backbone and the pendent groups exhibited UV-Vis absorption at a much longer wavelength than those with the conjugation only in the backbone or only in the side groups. The polymers with conjugated backbone need more space for chain stacking, and the conjugated backbone causes enhanced size of polymer particles assembled from solution. The results showed that primary microstructures of the polymer exerted significant influences on the physical properties.

Biogenic amino acid methionine-based corrosion inhibitors of mild steel in acidic media

N,N-Diallyl methionine ethyl ester hydrochloride 5 underwent alternating copolymerization with SO_2 via the Butler cyclopolymerization protocol in dimethyl sulfoxide(DMSO) to give water-soluble cycloterpolymer 6 with a ～1:1 molar ratio of sulfide and sulfoxide groups as a result of oxygen transfer from DMSO. Half of the sulfide groups in 6, upon oxidation with H_2O_2, afforded polymer sulfoxide 7 and polymer sulfone 8. The solution properties of these polymers were determined via a viscometric technique. The thermal stability of these polymers was determined by thermogravimetric analysis. The inhibition efficiency obtained from gravimetric mass loss, potentiodynamic polarization, and electrochemical impedance spectroscopy techniques agreed well with each other. The corrosion efficiencies increase with increasing concentration of the polymers. At a polymer concentration of 175 mM, the maximum inhibition efficiency of copolymer compounds 6–8 was determined to be 92%, 97%, and 95%, respectively. The synthesized polymer compounds acted as mixed-type inhibitors. Polymer compound 7 adsorbed onto the metal surface via chemisorption and physisorption and obeyed Langmuir, Temkin, and Freundlich adsorption isotherms. Analyses by X-ray photoelectron spectroscopy and scanning electron microscopy–energy-dispersive X-ray spectroscopy indicated that the adsorbed polymers formed a thin film on the metal surface and prevented further corrosive attack.

CARBAZOLE-CONTAINING HYPERBRANCHED POLY(ARYLENEETHYNYLENE)S:SYNTHESIS,CHARACTERIZATION,ANDPROPERTIES

New hyperbranched poly（aryleneethynylene）s containing carbazole moieties are synthesized in high yields （up to 87%） by polycyclotrimerization of 3,6-bis（4-ethynylphenyl）-9-octylcarbazole and its copolymerization with 1-octyne catalyzed by CpCo（CO）2 in THF. The structures and properties of the polymers are characterized and evaluated by IR, NMR, TGA, UV, photoluminescence, and cyclic voltammetry analyses. All the polymers are soluble in common organic solvents and show outstanding thermal stability （≥ 430℃）. They graphitize in high yields （up to 79%） when pyrolyzed at 800℃. Upon photoexcitation, the polymers emit a strong deep blue light of ca. 400 nm with quantum yields larger than 60%.

Disiloxane-Bridged Cyclopolymer as Polymer Dielectrics

We studied the dielectric properties of organosilicon-containing helical cyclopolymer PbMA which consists of PMMA main chains and tetramethyldisiloxane side rings. PbMA formed films with excellent uniformity through spin-coating onto highly n-doped silicon （n-Si） wafers for constructing devices of dielectric measurements, on which the dielectric properties and I-V characteristics of PbMA were studied. PbMA has a much lower dielectric constant （lower than 2.6） in the frequency range of 10-105 Hz, and better thermal stability than PMMA does. I-V data showed that the metal/PbMA/n-Si devices have different conducting directions, depending on whether Au or Al deposited over PbMA layers.

Cyclocopolymerization of 1,6-heptadiene with ethylene by half-sandwich scandium catalysts

The cyclocopolymerization of 1,6-heptadiene （HPD） with ethylene （E） by a series of half-sandwich scandium alkyl catalysts bearing various auxiliary ligands have been examined. Significant ligand influence on the copolymerization activity and selectivity was observed. In combination with one equivalent of [Ph3C][B（C6F5）4], the half-sandwich scandium dialkyl complexes bearing a Lewis base THF （1） or an NHC side arm （2） yielded the copolymer products together with cross-linked polymers in the copolymerization of HPD with ethylene. In contrast, the THF-free complexes Cp＇Sc（CH2C6H4NMe2-o）2 （3： Cp＇ = C5H5; 4： Cp＇ = CsMe4SiMe3） and the phosphine oxide side-arm containing complex （C5Me4SiMe2CH2（O）PPh2）Sc（CH2SiM%）2 （5） showed excellent activity and selectivity for the cyclocopolymerization reaction, without giving cross-linked products. The 1H and 13C NMR analyses revealed that the resulting copolymers consist of E-E sequences and six-membered ring methylene-1,3-cyclohexane （MCH） and five-membered ring ethylene-1,2-cyclopentane （ECP） units. The HPD content in the co- polymer products could be easily controlled by changing the feeding amount of HPD under 1 atm of ethylene.