Glass transitions in ethylene copolymers and vinyl homopolymers and copolymers

Abstract

In ethylene copolymers isolatedCH2CHRCH2 groups undergo a glass transition at about −10 to −50°C., the exact temperature depending upon the nature of R. For any given copolymer the temperature of the transition remains reasonably constant over a broad composition range at high ethylene contents. At high comonomer content the transition rises with composition along the line drawn between the glasstransition temperature of polyethylene and that of the homopolymer of the comonomer in question. A second glass transition is also observed in ethylene copolymers at about −125°C. over the whole composition range. This transition corresponds to motion of CH2 sequences of three to five or more in the main chain. The temperature position of this transition is usually independent of the nature of the rest of the chain. The behavior of ethylene copolymers is quite different from that of normal vinyl copolymers, where only a single glass transition is observed for each composition and where the temperature position of the transition changes uniformly with composition along the line drawn between the glass transitions of the respective homopolymers. It is concluded that the motions involved in the glass transitions of the main chain CH2 sequences and of isolated CH2CHRCH2 groups in ethylene copolymers are localized, involving only a few carbon atoms. In the case of the normal vinyl copolymers, on the other hand, the motion at the transition appears to be a long‐range motion involving a great many chain carbon atoms and cooperative motion of the pendent groups. This change in the nature of the motion involved at the glass transition in going from high ethylene content copolymers to low ethylene content or vinyl copolymers appears to arise because of steric hindrance and/or restrictive dipolar forces between the pendent groups of the CH2CHRCH2 segments in those cases were they are not isolated from each other. Finally, it is concluded that all vinyl homopolymers would have glass transitions in the −10 to −50°C. range if steric hindrance between the side groups did not occur. It is shown that as the pendent group becomes less bulky or is further separated from the main chain by CH2groups the glass transition temperature decreases presumably towards the −10 to −50° range characteristic of the transition of isolated CH2CHRCH2 groups.

Hyperbranched Acrylate Copolymer via Initiator‐Fragment Incorporation Radical Copolymerization of Divinylbenzene and Ethyl Acrylate: Synthesis, Characterization, Hydrolysis, Dye‐Solubilization, Ag Particle‐Stabilization, and Porous Film Formation

“…Temperature The observed results are also shown in Table (runs [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27].…”

“…The T g was much higher than that (À10 8C) of poly(EA). [27] This might be ascribed to the incorporation of the benzene units in the compact hyperbranched copolymers.…”

Physical properties and blend miscibility of hydrogenated acrylonitrile-butadiene rubber

“…The unexpected high T g of copolymers of ethylene with other vinyl monomers has long been observed in the literature. 18 It has been reported for ethylene-copolymers of vinyl acetate, vinyl chloride, and different acrylates. Other earlier investigations 6,12,13 have remarked on this behavior in HNBR.…”

Polymer class specificity of the glass temperature

“…It is interesting to notice that cooperative trans-gauche 'crankshaft' like motions in poly(ethylene) have been involved to explain the experimentally observed different characteristic 'freeze-in' processes of poly(ethylene) showing distinct T g values [17,18].…”