Design of Mechanically Robust High-T_g Polymers:  Synthesis and Dynamic Mechanical Relaxation Behavior of Glassy Poly(ester carbonate)s with Cyclohexylene Rings in the Backbone

Abstract

High-T g yet mechanically robust polymers are desirable but difficult to realize. To explore whether the insertion of a motionally active molecular entity in the backbone could produce polymers with both high T g and yet are not brittle, three series of high-T g glassy polycarbonates/polyesters/poly(ester carbonate)s were designed and synthesized. The secondary relaxation behavior of these polymers was studied by dynamical mechanical analysis (DMA). Incorporation of cyclohexylene groups (C-rings) in the main chain of polymers made from two rigid and bulky monomers, spirobiindane bisphenol (SBI) and trimethylcyclohexylbisphenol (Tmc), respectively, changes the γ relaxation process dramatically in peak shape and position in these polymers. No such change is observed in polycarbonate polymers made from cyclohexylbisphenol (BPAZ), or ZPC for short. Through monitoring the γ relaxation with gradual structural change, C-rings in the main chain backbone are proposed to undergo active ring inversion. The γ relaxation of ZPC is proposed to be mainly due to side-chain C-ring inversion. The narrowing on the high-temperature side of the γ relaxation peak of the polycarbonate of Tmc is proposed to be due to the restricted motion of its axial phenyl rings. A linear correlation between relaxation strength and total C-ring concentration was found for all the polymers.

Grafting Polymers from Poly(2,6-dimethyl-1,4-phenylene oxide) as New Thermoplastics

“…Most of them are engineering thermoplastics based on poly(phenyl esters) or poly(phenyl ketone), such as poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) ( l p ≈ 1.3 nm, T g = 211 °C), poly(bisphenol carbonate) ( l p ≈ 1.7 nm, T g = 150 °C), and so on. [1a,14] Graft polymer with semiflexible backbones may not only obtain the higher toughness over polymers with flexible backbones, but also could overcome the processing and synthetic problems in semirigid graft polymers. It is necessary to investigate such architectural advantages to design new thermoplastics.…”

“…It is necessary to investigate such architectural advantages to design new thermoplastics. Compared with semirigid polymers,[6d,15] these semiflexible polymers usually have lower T g , which are easier for processing in melt and solution,[14a,16] thus more convenient to prepare graft polymers.…”

Partially bio‐based poly(amide imide)s by polycondensation of aromatic diacylhydrazides based on lignin‐derived phenolic acids and aromatic dianhydrides: Synthesis, characterization, and computational studies

“…The calculated T g of PAI‐1 is 18 K higher than PAI‐4 as compared with an increase in 22 K observed in DMA studies. It is generally accepted that T g of an amorphous polymer is determined by α relaxation or segmental motion of the chains, which in turn is affected by the free volume and/or rigidity of the chains. The availability of more free volume and less chain rigidity leads to faster relaxation resulting in lower T g and vice versa.…”

“…To analyze the segmental relaxation, dihedral autocorrelation function C ( t ) was calculated as follows: where α ( t ) and α ( t + Δ t ) denote the torsional angle at time t and time t + Δ t , respectively. The time‐scale of decay of C ( t ) gives a measure of the rigidity of chains, where a longer time‐scale would signify increased rigidity . The comparison of C ( t ) for both PAI‐4 and PAI‐1 is shown in Figure .…”

Sustainable Polycarbonates from a Citric Acid-Based Rigid Diol and Recycled BPA-PC: From Synthesis to Properties

“…In this work, in order to improve the toughness and compensate for the low reactivity of OPD, while at the same time retaining the rigidity of OPD-based PCs, BHEEB is incorporated in the polymer chains by melt polymerization with OPD in different molar ratios. Previous investigations suggested that the high impact strength of BPA-PC can be attributed to its capacity of absorbing high impact energy which, in turn, has been correlated with secondary relaxations involving cooperative motions of BPA units in the polymer chains . It is worthy to note that although BPA is toxic, however, BHEEB is biocompatible.…”