Decheng Wan

Transformation of copolymerization mechanism of N-phenyl maleimide and ethyl phenylacrylate in the mixture of dioxane and pyridine

The copolymerization of N-phenylmaleimide (NPMI) with ethyl phenylacrylate (EPA) in a mixture of dioxane (DIO) and pyridine (Py) was investigated. The apparent monomer reactivity ratio r1 (NPMI) = 0.07 ± 0.01 and r2 (EPA) = 0.09 ± 0.02 in DIO was turned to r1 (NPMI) = 3.67 ± 0.07 and r2 (EPA) = 0 ± 0.03 in Py. The copolymerization of NPMI and EPA with the fixed feed ratio (mol/mol 1 : 1) in different volume ratio of DIO/Py showed that the copolymer composition might be varied in a wide range from the 93.5% of NPMI contents in copolymer to 48.7%. When the volume fraction of Py in the mixture of DIO and Py was 10%, the following two kinds of copolymers were formed: a copolymer in which the content of NPMI increased with the Py and the copolymerization also could be inhibited by hydroquinone and a copolymer with low molecular weight almost completely composed of homopolymer of NPMI and is not affected by radical inhibitor as hydroquinone. The transformation of the copolymerization mechanism from the radical to anionic, which was dependent on the volume ratio of DIO and Py, was suggested.

Spontaneous alternating copolymerization of N-phenylmaleimide with ethyl α-phenylacrylate

The spontaneous copolymerization of N-phenylmaleimide (NPMI) (M 1 ) with ethyl α-phenylacrylate (EPA)(M 2 ) were carried out in dioxane at 85°C. A high alternating tendency was observed. The monomer reactivity ratios were r 1 = 0.07 ± 0.01 and r 2 = 0.09 ± 0.02. The maximum copolymerization rate and molecular weight occurs at 70-80 mol% (M 1 ) in feed ratio. The spontaneous alternating copolymerization is considered to be carried out via a contact-type charge transfer complex (CTC) formed between the monomers. Thermogravimetric analyses (TGA) indicate the resulting copolymers have high thermal stability.

Aggregation of 2‐ethylacrylic acid in dioxane and its effect on the radical copolymerization of maleimide with 2‐ethylacrylic acid

Radical copolymerization of maleimide (MI) with 2-ethylacrylic acid (EAA) in dioxane using 2,2-azo-isobutyronitrile (AIBN) as an initiator at 60°C was investigated. The monomer reactivity ratios were determined by the Kelen-Tudos method, and r 1 for MI and r 2 for EAA are 0.07 and 1.00, respectively. It was found that the aggregates of EAA with dioxane exert great effect on the copolymerization. The thermal degradation process of the copolymers might be divided into two steps,. In the first step intramolecular dehydration of EAA segments was conducted and anhydride was formed. In the second step, crosslinking occurred and the copolymers no longer dissolved in any solvent. The activation energy of each stage was calculated according to Broidos method. In the first stage the degradation activation energy increases with the EAA content in the copolymers due to the association of adjacent EAA segments.

Preparation of PMMA–PS–PMMA via combination of anionic and photoinduced charge‐transfer polymerization

PMMA–PS–PMMA triblock copolymers were prepared by the combination of an anionic mechanism with charge-transfer polymerization. Polystyrene with aromatic tertiary amino groups at both ends (PSba) was synthesized first by the reaction of a living polystyrene macrodianion with excess p-(dimethylamino)benzaldehyde; then, the PSba was constituted into a binary system with benzophenone (BP) to initiate the polymerization of methyl methacrylate (MMA) under UV irradiation. The intermediate and resulting block copolymers were characterized by GPC, IR, and 1H-NMR.

Controllability of radical copolymerization of maleimide and ethyl α-(n-propyl)acrylate using 1,1,2,2-tetraphenyl-1,2-bis(trimethylsilyloxy) ethane as initiator

The radical copolymerization of maleimide (MI) and ethyl a-propylacrylate was performed using 1,1,2,2-tetraphenyl-1,2-bis(trimethylsilyloxy) ethane (TPSE) as initiator. The whole copolymerization process might be divided into two stages: in the first stage, the copolymerization was carried out on the common radical mechanism, the molecular weight of the copolymer increased rapidly in much lower conversion (, 85%), and did not depend on the polymerization time and conversion; in the second stage, molecular weight of the copolymer increased linearly with the conversion and the polymerization time. It was found, however, when the conversion was higher than a certain value, for example, more than 36%, the molecular weight of the copolymer was nearly unchangeable with the polymerization time and the molecular weight distribu- tion was widened. The effect of reaction conditions on copolymerization was discussed and the reactivity ratios were calculated by the Kelen-Tudos method, the values were rMI 5 0.13 6 0.03, rEPA 5 0.58 6 0.06 for TPSE system and rMI 5 0.12 6 0.03, rEPA 5 0.52 6 0.06 for AIBN system.