Yan Deyue

Calculation of the mean-square radius of gyration for polymer chains with side-groups

Abstract The mean-square radius of gyration of polymer chains with side-groups was formulated using the method of matrix algebra with the rotational isomeric state approximation. If the effect of the side-groups is neglected, the expression reduces to that reported by Flory. The molecular weight dependence of the root-mean-square radius of gyration for isotactic polypropylene was obtained as S 2 1 2 =0.34M 1 2 p] in fair agreement with experimental data from small-angle neutron scattering, reported by Ballard et al.

Reverse atom transfer radical polymerization of methyl methacrylate initiated by AIBN/FeCl3/isophthalic acid systèm

The reverse ATRP of MMA using AIBN/FeCl3/ isophthalic acid as the initiating system was successfully performed. The new initiating system can be used to synthesize PMMA with high molecular weight and narrow polydispersity index. The polymerization shows ‘living’/controlled characteristics. Compared with other initiating system used in reverse ATRP, the easy availability and non-toxicity of isophthalic acid make it very attractive.

Investigation on the Brill transition of polyamide 618

The Brill transition of even-even polyamide 618 was investigated using differential scanning calorimetry (DSC), temperature-dependent wide angle X-ray diffraction (WAXD) and Fourier transform infrared (FTIR). The X-ray diffraction results indicate that the melt-crystallized sample of polyamide 618 transforms from the triclinic unit cell to the pseudo-hexagonal phase in the range of 120–180°C. In this range, the thermograph of polyamide 618 presents a broad endothermal peak. From the FTIR spectra, it was found that during the transition process of polyamide 618, the intensity of the intra-sheet hydrogen bonds becomes weak. At the same time, the CH2-amide bonds twist, and the all-trans conformation of methylene sequences is disordered by inserting the gauche conformation. The CH2 segments are in a mobile state because of the enhanced stretching and twisting vibrations of the C-CO and C-N bonds.

Synthesis and characterization of organosoluble aromatic copolyimids

A series of aromatic copolyimides was successfully synthesized from the commercial pyromellitic dianhydride (PMDA) with a commercial diamine p-phenyldiamine (PDA) and a diamine 4,4′-methylenebis-(2-tert-butylaniline) (MBTBA) specially designed by the authors. The copolyimides were characterized by Infra-red (IR), Nuclear Magnetic Resonance (NMR), Gel Permeation Chromatography (GPC), Ultraviolet Visual (UV-Vis), Thermogravimetic Analysis (TGA) and Dynamic Mechanical Analysis (DMA). The copolyimide was precipitated in m-cresol in the polymerization process when the molar ratio of MBTBA and PDA was lower than 6/4. The number-average molecular weight of the soluble copolyimides measured by GPC was larger than 4.0 × 104, and the polydispersity index was higher than 1.5. Only one glass transition temperature of these copolyimides was detected around 360°C by DMA. The copolyimides did not show appreciable decomposition up to 500°C under N2, and the thermal stability of the copolyimide increased a little with the introduction of PDA into the polyimide main chain.