On the glass transition temperature of comblike polymers: Effects of side chain length and backbone chain structure

Abstract

Polymers composed of monomer units that contain n‐alkyl side chains are characterized by a monotonical decrease in the glass transition temperatures toward a critical value (Tg)c as the number of C atoms in the side chain increases toward a corresponding critical value nc. Thus the glass transition temperatures of these comblike polymers are for a given backbone chain structure directly related to the molecular weight (M) of the monomer unit. This relationship can be represented by the differential equation dTg/dM = −k′M[Tg − (Tg)c], which on integration yields Tg = (ΔTg)0 exp−[k(M2 − M 12)] + (Tg)c, where (ΔTg) = (Tg)1 − (Tg)c, and the subscript 1 refers to n = 1. Values for Tg calculated according to this relationship are in good agreement with published data on polybutadienes, polystyrenes, poly(vinyl ether)s, polyacrylates, polymethacrylates, polyitaconates, poly(phenylene ether)s, and poly(N‐maleimide)s. For these polymers the critical quantities nc and (Tg)c can be estimated rather well by the simple relationships nc = 1 + 2.8 × 10−2 (Tg)1 and (Tg)c = (Tg)1 − nc(nc − 1). The Tg(M) relationship derived appears to be applicable also to copolymers that contain monomer units with alkyl side chains.

Cellulose Acetate‐graft‐Poly(hydroxyalkanoate)s: Synthesis and Dependence of the Thermal Properties on Copolymer Composition

“…M c ¼ 775-1 258, evaluated for the present copolymers, are considerably large in comparison with the corresponding values for the comb-like polymers, [20] in the main-chain construction. In addition, the degree of semi-flexibility of the PHA side-chains is higher relative to that of alkyl side-chains, which may be partly responsible for the observation of larger M c s for the present copolymer system.…”

“…In analogy with a T g analysis performed for the comblike polymers, [20] by denoting for the copolymer system considered with M the molecular weight of a monomer unit which contains a pendant PHA side-chain of MS ¼ N, and with (T g ) c the glass transition temperature at M ¼ M c corresponding to MS ¼ N c , the T g as a function of M for the M M c (or N N c ) portion of the curve in Figure 3 may be represented by the following differential equation:…”

“…The K values calculated for the CA-graft copolymers are much smaller, by one or two orders of magnitude, than those for the comb-like polymers providing average Ks of 6.00 Â 10 À4 (PAB), 0.65 Â 10 À4 (PAS), 1.45 Â 10 À4 (PAVE), 1.60 Â 10 À4 (PAA), 0.97 Â 10 À4 (PAMA), 0.38 Â 10 À4 (PAPE) and 0.55 Â 10 À4 (PAM). [20] The physical meaning of K is still unclear and cannot be simply correlated with a specific structural parameter. At least, however, the smaller K values for the graft copolymers indicate that a larger M is required to reduce T g in the T g -M plot (see Equation (10) and (11)), reflecting the comparatively stiff nature of both the CA backbone and the PHA ester linkage.…”

Some properties of copolymers of vinylidene chloride with acrylates and methacrylates, Part 1

“…In every copolymer series, polar interactions between VDC and acrylic ester units in the polymer chain having high VDC contents lead to stiffening and thus to an increase in the glass transition temperature 9,15) . At even higher acrylate concentrations, the ester group acts as an internal plasticizer and the glass transition temperature drops again 13,16) . Comparing the various copolymers, the maximum in the glass transition temperature is shifted to higher VDC concentrations in the copolymer, the longer the ester group (Tab.…”

Bis(dialkylamino)‐substituted isopropenyltriazines: effect of the length of the alkyl chains on the polymerization as well as on the properties of the resulting comb‐like polymers

“…In particular, the ability of side-chain crystallization has been actively investigated ' 9 [12][13][14][15][16][17]. The crystallization behavior results in a dramatic change of mechanical properties 'vz, 18-20) and gas permeability2'.…”