Glass‐transition temperatures and rheological behavior of methyl methacrylate–styrene random copolymers

Abstract

Poly(methyl methacrylate-ran-styrene) copolymers were synthesized under monomer-starved conditions by emulsion copolymerization. The glass-transition temperatures (T g 's) of the copolymers were measured by differential scanning calorimetry (DSC) and torsional braid analysis (TBA). The results showed that the methyl methacrylate-styrene random copolymers produced an asymmetric T g versus composition curve, which could not even be interpreted by the Johnston equation with different contributions of dyads to the T g of the copolymer considered. A new sequence distribution equation concerning different contributions of triads was introduced to predict the copolymer's T g . The new equation fit the experimental data exactly. Also, the T g determined by TBA (T gTBA ) was higher than the one determined by DSC (T gDSC ) and the difference was not constant. The rheological behavior of the copolymers was also studied. T gTBA Ϫ T gDSC increased with increasing flow index of the melt of the copolymer, and the reason was interpreted.

Thickness and composition dependence of the glass transition temperature in thin random copolymer films

“…The PS-PMMA random copolymers with various fractions were synthesized by emulsion or suspension polymerization. Previous investigations reported that the random copolymer followed an asymmetric T g versus composition curves, which cannot be adapted by the Fox or Gordon -Taylor equations by the different formation of diad-and triad-sequences [26]. Although Fox equation does not predict an exact value of T g in copolymer, it can estimate T g decreasing tendency with thickness in Fig.…”

Thermal properties and side chain crystallinity of styrene and n‐alkyl methacrylate terpolymers

“…and , glass transition of the investigated copolymers is weakly expressed, stretches over a wide temperature range and without a clear completion exceeds into endothermic peak. Since the glass transition is a relaxation process , in accordance with conventional means of analysis , it can be defined by several temperature values (Fig. ).…”

“…). Nonlinear dependence of T g on the composition of copolymers (copolymers that display a maximum or a minimum T g for a certain copolymer share) usually is described by equations : …”

“…It is assumed that the glass transition temperature depends on the stiffness of copolymer chain, and that the contribution of each dyad is proportional to the number of chemical bonds with the possibility of rotation. The deviation from linearity when it comes to the dependence of T g on composition is often associated, mainly qualitatively, with the molecular interaction of copolymeric system . In the above equations, denotes the molar proportion of type ij dyad in the copolymer, where T g, ij presents the glass transition temperature of corresponding dyad ij .…”

P(N-Phenylmaleimide-Alt-Styrene) Introduced with 4-Carboxyl and Its Effect on the Heat Deflection Temperature of Nylon 6

“…Heat deflection temperature ( HDT ) is a widely employed parameter for quality control and material development in industry and can be taken as the material’s ultimate use point. In order to improve the HDT , NPMI derivatives and their copolymers have attracted considerable interest with respect to applications in acrylonitrile butadiene styrene (ABS) [15] and poly(vinyl chloride) (PVC) [16,17]. Jianting Dong and his co-workers [11,12,13,14,15] synthesized an N -phenylmaleimide (NPMI)-styrene(St)-maleic anhydride (MAH) copolymer (NSM copolymer), and found that the Vicat softening point temperature of the ABS/NSM blend was significantly enhanced by increasing the NSM content.…”