Interfacial synthesis and characterization of random and segmented block bisphenol A–tetrabromobisphenol A copolycarbonates

Abstract

SYNOPSISThe chain sequence architecture of bisphenol A-tetrabromobisphenol A copolycarbonates depends on the process employed to prepare them. An interfacial process involving a singlestep phosgenation produces a segmented block copolymer, contrary to previous assumptions. An interfacial two-step phosgenation process allows the preparation of random copolycarbonates. In each process the control of the pH of the aqueous phase of the two phase reaction mixture is required to achieve complete comonomer conversion to copolymer and to obtain the desired sequence architecture. The chain sequence architecture of these copolycarbonates can be estimated by examination of their Fourier transform infrared spectra. The relative bandwidth of the carbonate stretching band is roughly proportional to the copolycarbonate number average sequence length, allowing the facile distinction between block and random copolymers. The number average sequence lengths of these copolycarbonates were quantified by carbon-13 NMR spectroscopy. These analyses showed that the one-step phosgenation process yields segmented block copolycarbonates having number average sequence lengths from about 4 to 9, and the two-step phosgenation process produces random copolycarbonates having sequence lengths from 1.6 to 2. The distribution of the aromatic carbon triads of these random copolymers shows them to have an alternatesegmented block architecture, which is consistent with the synthesis conditions, rather than a statistically random distribution of comonomer segments. Dynamic mechanical analysis of two of these copolycarbonates shows a dependence of their low temperature secondary transitions on the copolymer sequence structure. A segmented block copolycarbonate, having a number average sequence length of about 4, displays two distinct peaks in its tan 6 curve at temperatures corresponding to those transitions observed in the respective homopolymers. The tan 6 curve of a random copolycarbonate shows a single low temperature secondary transition midway between those of the homopolymer. 0 1994 JohnWiley & Sons, Inc.

Effect of Linkage Groups on Motional Cooperativity in the Secondary Relaxations of Some Glassy Polymers

“…By calculating the integrals of these NMR peaks corresponding to different diads, we were able to estimate the relative amount of different diads. On the basis of the following equations 18,24 where L nB is the number-average sequence length of BPA segments, L nT the number-average sequence length of TMBPA segments, N BB the relative amount of BB diad, N BT the relative amount of BT diad, and N TT the relative amount of TT diad. The number-average sequence length of BPA segments and TMBPA segments in the copolyformal was characterized.…”

“…The number-average sequence length was estimated by analyzing the diads in the copolymers. 18,24 In the copolyformal chain, there are three types of diads: BB, TT, and BT (shown in Figure 3). We chose the hydrogens where L nB is the number-average sequence length of BPA segments, L nT the number-average sequence length of TMBPA segments, N BB the relative amount of BB diad, N BT the relative amount of BT diad, and N TT the relative amount of TT diad.…”

“…On the basis of this result, they concluded that the secondary relaxation of BPA-PC is a cooperative motion and the molecular motion extends to seven repeat units. Later, Marks 18 investigated the secondary relaxation behavior of the copolycarbonates based on BPA-PC and tetrabromobisphenol A PC. He also found that the secondary relaxation behavior of the copolymers is strongly dependent on the block length and arrived at a similar conclusion.…”

“…The chemical structures of BPA-PC and BPA-polyformal (PF), as shown in Figure , are exactly the same except for the linkage groups. Following Xiao and Marks' approach, , we synthesized a series of copolyformals with controlled sequence structure and investigated the linkage effect by comparing DMA results of polyformals to that of polycarbonates.

1 Chemical structure of BPA-PC and BPA-PF.

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Preparation and properties of flame-retardant polyphosphate esters: Low-temperature solution polycondensation of 3,3,?5,5?-tetrabromobisphenol AF and aryl phosphorodichloridates

“…The same results have also at 700ЊC in nitrogen. Figure 2 shows an example of polyphosphates with a 10ЊC min 01 heating rate been found by Marks 42 and Liaw and Chang 25 for copolycarbonates based on TBBPA and TBPAF, re-in nitrogen. The degradation of all polymers occurs in a two-step process.…”