Alan Bunn

Sulphonation of poly(phenylene ether sulphone)s containing hydroquinone residues

Abstract Analysis, mainly by n.m.r. spectroscopy, shows that when copolymers comprising phenylene-ether-phenylene-sulphone and phenylene-ether-phenylene-ether-phenylene-sulphone repeat units are dissolved in 98% sulphuric acid, the ether-phenylene-ether groups are monosulphonated completely, but the other phenylene groups remain unchanged. Thus, sulphonation of these copolymers in this way provides a simple technique for preparing poly(phenylene ether sulphone)s sulphonated to a predetermined extent. The solution viscosities, glass transition temperatures and water up-take of the sulphonated copolymers increase as the extent of sulphonation is increased.

Unsaturated polyesters based on terephthalic acid: 4. Sequence distribution of crosslinks in styrene cured resins

Abstract The sequence distribution of the styrene crosslinks in a cured polyester formed from propylene glycol, terephthalic acid and maleic anhydride has been studied by 13 C nuclear magnetic resonance and infrared spectroscopy. The n.m.r. method involved the degradation of the crosslinked polyester into a copolymer of styrene and fumaric acid and the interpretation of the peaks in the 13 C spectrum, which arise from the quaternary phenyl carbon atoms in sequences of styrene units, by considering the 13 C spectra of copolymer standards of styrene and diethyl fumarate. The crosslinking process was monitored directly by infra-red spectroscopy, and the distribution of sequence lengths of styrene units was then estimated by considering that crosslinking may be interpreted by a statistical treatment of copolymerization. Values of mol fractions of styrene units in sequences of monads, diads and triads determined by 13 C n.m.r. and infra-red spectroscopy were in fair agreement.

Substituent effects in the 13C n.m.r. spectra of aryl ether copolymers: 5. Aryl ether ketone copolymers in acid solution

Abstract Complete assignments have been made for the quaternary carbon signals in the acid solution 13C n.m.r. spectra of three statistical copolymers of the aryl ether ketone unit with aryl ether ether ketone (EK/EEK), aryl ether ketone ketone (EK/EKK) and aryl ether sulphone (EK/ES). These signals are extremely sensitive to sequencing information and the spectra obtained can only be explained by considering functionality variation up to six rings removed from the observed carbon atom, C∗. The transmission medium for these long range effects is the π electron system of the chain, as evidenced by the enhanced effects if the chain through which they are transmitted consists of alternating ether and ketone bridges, the most efficiently conjugated system. The effects are removed or diminished by insertion of other functionalities and there is also a correlation between the absolute chemical shift of C∗ and the size of splitting and amount of fine structure observed.

Substituent effects in the 13C nuclear magnetic resonance spectra of aryl ether copolymers: 4. Materials containing sulphonated aryl rings

Abstract Polymeric materials containing 1,4-disubstituted aryl rings with ether (E), ketone (K) and/or sulphone (S) linkages, and in which certain rings are monosulphonated, give extremely complex 13 C nuclear magnetic resonance (n.m.r.) spectra. The quaternary carbon atom shifts, which are particularly sensitive to changes in the monomer sequences and sulphonation pattern, have been assigned to specific sequences and pattern differences, with signals characterized by either ortho or meta sulphonation of rings up to three rings distant from the observed carbon atom (C∗) being resolved. The shifts obtained for the sulphonated ES/EES copolymer, when compared with those of the non-sulphonated material, suggest the major transmission mechanism for sulphonation effects to be via the π system, with a possible anisotropic effect contributing to the longer-range shifts, induced by the specific conformation the chain adopts. This argument leads to a full assignment, including specific sulphonation patterns, of the sulphonated ES/EES copolymer 13 C n.m.r. spectrum in deuterated dimethylsulphoxide (DMSO-d 6 ).

Substituent effects in the 13C nuclear magnetic resonance spectra of aryl ether copolymers: 2. Ether sulphone/ether ether sulphone and ether sulphone/ether ketone copolymers in deuterated dimethylsulphoxide

Abstract The 13 C nuclear magnetic resonance signals for the quaternary carbon atoms in aryl ether sulphone/aryl ether ether sulphone (ES/EES) and aryl ether sulphone/aryl ether ketone (ES/EK, 50:50) copolymers in deuterated dimethylsulphoxide (DMSO-d 6 ) solution have been assigned to particular monomer sequences. Based on a poly(aryl ether) chain having a quaternary carbon, C∗, of chemical shift Δ 0 (ppm), the effect of replacing O with SO 2 in a particular position has been evaluated for the ES/EES copolymer system. Positive shifts are found for all substitutions anti ( para ) to C∗; conversely negative shifts occur for all syn (connected) substitutions. In each case, the absolute magnitude of the effect decreases with distance from C∗. Measurable effects were observed for sulphone groups separated from C∗ by up to four benzene rings. Sufficient data were available to calculate a value for Δ 0 and this is in good agreement with experimental values. The sulphone parameters were used in the ES/EK spectrum to allow calculation of a series of ketone parameters. The latter effects are similar in nature to the sulphone effects (i.e. positive in one direction, negative in the other) but lower in absolute magnitude for each position other than the α position, in which the function is bonded directly to C∗. The calculated ketone effects were used to predict chemical shifts in an ether ketone system, allowing a comparison with experimental data.

Substituent effects in the 13C n.m.r. spectra of aryl ether copolymers: 3. The effect of biphenyl functionality

Abstract The 13C n.m.r. quaternary carbon signals observed in the DMSO-d6 solution spectrum of the aryl ether sulphone/aryl ether biphenyl (ES/E−) copolymer have been assigned to specific monomer sequences. The effect of a biphenyl unit at a particular site in the chain has been evaluated and these parameters, in addition to similar sets previously obtained for the sulphone functionality, have been used to calculate chemical shifts in several other biphenyl-containing copolymers. The deviation from experimental shifts has been rationalized in terms of the conformation of the biphenyl function and, in conjunction with known conformational preferences of sub-units in the copolymers, in an assessment of the overall molecular conformation.

Substituent effects in the 13C n.m.r. spectra of aryl ether copolymers. 6. Sulphonated aryl ether ketones

Abstract Assignments have been made for the EK′α,a′-diad quaternary carbon signals in both the acid and DMSO-d 6 solution 13 C n.m.r. spectra of the sulphonated aryl ether ketone/aryl ether ether ketone copolymer (sEK/EEK). Signals have been assigned to specific monomer sequences and sulphonation patterns with the latter information (in acid solution) derived from a consideration of the end group signals in the 13 C spectrum of a low molecular weight, fluorine ended poly(aryl ether ether ketone), F-sPEEK. Comparison of the spectra of sEK/EEK in the two media with the corresponding spectra of the non-sulphonated polymer (using, in the latter case, calculated shifts for the DMSO solution spectrum) indicates the chemical shift changes caused by sulphonation to be considerably different in the two solvents. Thus on sulphonation the signal range is expanded in DMSO and contracted in acid solution and, furthermore, if sulphonation in a specific position causes a lowfield shift of the observed carbon atom, C∗, in DMSO the equivalent effect will be to highfield in acid (and vice versa ). This is interpreted in terms of a greater similarity of the π systems in DMSO and acid solution when the material is sulphonated, compared to the unmodified EK/EEK. The level of carbonyl protonation in sulphuric acid is, therefore, much reduced from that in a non-sulphonating acid.