Quantitative valuation of composition in vinylformal,vinylacetate and vinylalcohol ter-copolymers by1H- and13C-n.m.r. spectroscopy

The¹³C-n.m.r. signals were assigned to the composing structural groups of the copolymers. The composition of the copolymers was determined by¹³C n.m.r. using the NOE extinction technique. The analyzed samples were synthesized under normal and relatively mild reaction conditions. Despite this and purification methods that avoided elevated temperatures, it was not possible to find hemiformal groups in any amount. Therefore it is possible to analyze these copolymers composed of formal, vinylacetate and vinylalcohol structural groups in a relatively easy way by means¹H n.m.r.     

Monomer sequence determinations of aryl ether sulphone copolymers as determined by 13C n.m.r.

The monomer sequence distributions of three types of aryl ether sulphone copolymers have been determined by ¹³C n.m.r. spectroscopy. Two amorphous aryl ether sulphone copolymers were shown to have transetherified (or ether interchanged) during polymerisation to become random copolymers. The residues in these copolymers were (i)—OøOøSO₂øS—and (ii)—OøSO₂øøSO₂ø—-where ø denotes 1,4-phenylene. Copolymers of 50:50 aryl ether sulphone and aryl ether ketone made from different combinations of monomers were found to have different solubilities in dimethyl sulphoxide, and from ¹³C n.m.r. data this was shown to correlate with the amount of transetherification which had taken place during the polymerisations. The ¹³C n.m.r. chemical shifts for some of the carbon nuclei in these polymers were sensititive to functional groups situated even as far away as three or four aromatic nuclei along the polymer chain.     

Alkyl aryl ethers in lignite solubilization: 2. Analysis of oil fractions

The FT-i.r. and ¹H n.m.r. spectroscopic analyses of oils or maltenes from a Spanish lignite (Utrillas, Teruel), are reported. These oils were obtained by depolymerization with alkyl aromatic ethers (anisole, 3-methylanisoleand 1,3-dimethoxybenzene) catalyzed by Lewis acids ZnCl₂, AlCl₃, SbCl₃and BF₃ (as boron trifluoride etherate), at atmospheric pressure and temperatures <220 °C. Bands due to aromatic ethers in the i.r. and n.m.r. spectra of the oils obtained by depolymerization indicate solvent incorporation. Oils obtained by direct lignite extraction showed 25% aromatic H and some H_α (≈3%) without OH groups. These appeared in some oils obtained by depolymerization with AlCl₃ and were due to secondary reactions with the aromatic extract. Oils derived from processes with good yields showed increases in aromaticity. The extent of substitution of aromatic rings in oils obtained by depolymerization was less than for oils directly extracted. All the oils studied show a low degree of condensation.     

Syntheses and properties of novel copolymers of polycaprolactone and aliphatic polycarbonate based on ketal-protected dihydroxyacetone

The random copolymers of ε-caprolactone (CL) and 2,2-ethylenedioxy propane-1,3-diol carbonate (EOPDC) were synthesized in bulk at 120 °C using Sn(Oct)₂ as a catalyst. The poly(EOPDC-co–CL)s obtained were characterized by FT IR, ¹H NMR, ¹³C NMR, GPC and DSC. The copolymers were obtained with yield of 84.2–97.8 %. The number-average molecular weight of the copolymer is 2.75–7.76 × 10⁴ with a polydispersity of 1.52–1.68. The properties of the copolymer including the enzymatic degradation by Pseudomonas Cepacia lipase and drug-controlled release property were also investigated. The results showed that the copolymers are degradable at physiological conditions, and their degradation rate and release of Tegafur in the copolymers increase with increasing CL content in the copolymers.     

Copolymerization of acrylamide with sulphur dioxide. Determination of the effect of copolymerization temperature on the monomer sequence distribution by 13C n.m.r.

Acrylamide was copolymèrized with sulphur dioxide at temperatures from ?78° to 60°C. The bulk monomer composition was fixed at 60 mol % sulphur dioxide, and both azobisisobutyronitrile and ⁶⁰Co gamma radiation were used as initiators. The ratio R of acrylamide to sulphur dioxide in the copolymers increased as the copolymerization temperature was raised; for example R was 1.97 at ?78°C and 29.3 4at 60°C. The microstructure of the copolymers was determined by ¹³C-{¹H} n.m.r. The carbonyl resonances were the most sensitive to structure, and they were assigned to monomer sequence pentads and configurational sequence dyads and triads. Only the backbone carbon resonance areas were quantitatively reliable under the observing conditions. The methine and methylene carbons revealed monomer sequence triad structure, and their relative areas allowed the monomer sequence distribution to be obtained as a function of temperature. A propagation-step mechanism was proposed to account for the effect of temperature on the monomer sequence distribution. No 1:1 alternating sequences were formed above 0°C, and this result suggested that depropagation of the sulphonyl radical was particularly facile when there was a pen-penultimate sulphone unit in the terminal chain sequence. The results were compared with those from other systems which form variable-composition polysulphones.     

Biodegradable polymers for use in surgery — poly(ethylene oxide)/poly(ethylene terephthalate) (PEO/PET) copolymers: 2. In vitro degradation

The degradation mechanism of a series of poly(ethylene oxide)/poly(ethylene terephthalate) (PEO/PET) copolymers, synthesized as described in Part 1¹, has been studied in vitro. The need for the development of in vitro test methods for candidate biomaterials is set down. The effect of time, temperature, pH and selected enzymes on the rate and mechanism of degradation is elucidated. The degradation products are identified. The degree of degradation was monitored molecularly by gel permeation chromatography (g.p.c.) and end-group titration techniques. The composition of the copolymers was obtained using infra-red (i.r.) and nuclear magnetic resonance (n.m.r.) spectroscopy. Mass loss and water uptake data are also given. The mechanism of degradation is shown to be by hydrolysis. The effect of ethylene oxide (EO) and ⁶⁰Co γ-irradiation sterilization on the copolymers was investigated.     

Graded block and randomized copolymers of butadiene-styrene

Graded block and randomized copolymers of butadiene-styrene were prepared anionically by polymerizing a mixture of butadiene and styrene with n-BuLi, in the absence and in the presence of t-BuOK respectively. Determination of the monomer composition and microstructure of the poly-butadiene sequence was achieved by 300 MHz ¹H n.m.r. and infra-red spectroscopy. ¹H n.m.r. equations developed previously for butadiene-styrene copolymers were modified and extended. In this way, cis, trans butadiene contents were determined from the aliphatic region of the n.m.r. spectra. The monomer sequence distribution of the copolymers has been investigated by examination of the morphology and their dynamic mechanical properties. The experimental conditions have been established for the preparation of random copolymers with inter- and intramolecular composition distribution.     

Determination of carbon C,CH, CH2 and CH3 group abundances in liquids derived from petroleum and coal using selected multiplet 13C n.m.r. spectroscopy

Selected, multiplet C n.m.r. spectra are obtained for three test samples deriving from petroleum and coal sources, by combining gated spin echo (GASPE) and conventional spin echo ¹³C n.m.r. procedures. Each selected multiplet spectrum contains resonances due to only one of the following groups: aromatic C or CH or aliphatic C, CH, CH₂orCH₃. In general artifacts contribute only minor intensity to individual spectra, with the separation between aliphatic CH and CH₃ spectra being the most difficult to achieve. Each spectrum can be integrated to yield the relative abundances of CH_n groups (n = 0 to 3). Selected multiplet ¹³C n.m.r. spectra provide a more detailed view of the component hydrocarbon groups in fossil-fuel derived materials than can be deduced from conventional ¹³C n.m.r. spectra.     

Molecular motion in α-methylstyrene and styrene-alkane copolymers studied by 13C n.m.r. spectroscopy

The temperature dependence of the ¹³C n.m.r. relaxation times are reported for a series of copolymers formed between methyl styrene or styrene and various α, ω-alkyl dihalides. The polymers studied contained alkyl blocks with n (the number of CH₂ units) varying from 0–10. The relaxation data indicates that the motion of both the styrene and the alkyl blocks change with the value of n. A comparison of the ¹³C relaxation data with that obtained from ultrasonic relaxation measurements supports the hypothesis that in the higher members of each series the alkane chain moves essentially independently of the ‘styrene’ moiety. The variation in the activation energy of the relaxation of the styrene moiety reflects in part a decoupling of the neighbouring phenyl group motion, as a consequence of the introduction of the alkane block.     

A-B-A-Triblock and multiblock copolyesters prepared from ε-caprolactone, glycolide and l-lactide by means of bismuth subsalicylate

Bismuth (III) subsalicylate, a commercial drug, was used as catalyst for 1,4-butanediol-initiated copolymerizations of ε-caprolactone (εCL) and glycolide (GL). Telechelic copolyesters having two OH-endgroups and predominantly alternating sequences were obtained. These copolyesters are amorphous with glass transition temperatures (T_gs) below −30 °C. In a second series of polymerizations, in situ chain extension with l-lactide (LLA) was performed, whereby A-B-A triblock copolymers were obtained without significant transesterification between A- and B-blocks. Finally, these A-B-A triblock copolymers were transformed into multiblock copolymers by chain extension with 1,6-hexamethylene diisocyanate. The block copolymers were characterized by ¹H and ¹³C NMR spectroscopy, by viscosity, SEC and DSC measurements.     

Motional restrictions and chain conformation in various swollen crosslinked polystyrene gels from 1H n.m.r. line-shape analysis

¹H high resolution (HR), broad-line (BL) and magic-angle rotation n.m.r. spectra of polystyrene crosslinked with 2–10 mol% divinylbenzene or ethylene dimethacrylate, swollen to equilibrium in CCI₄, CDCI₃ and benzene, were measured. The spectra were analysed as a folding of a narrow line-shape function approximated by the MAR n.m.r. spectrum, and an orientation-dependent dipolar broadening function. A molecular interpretation of the parameters obtained is presented. From MAR n.m.r. spectra, the rate of conformational transition depends on solvent, temperature and degree of crosslinking, but it remains very rapid even at 10% crosslinking. The second moment of the dipolar broadening function depends on the degree of crosslinking and is almost independent of temperature and solvent. The linear dependence of the dipolar broadening parameter on degree of crosslinking indicates that, in gels swollen to equilibrium, the statistical-average conformation of inter-crosslink chains is independent of their length, and is equal to that of linear polystyrene chains in dilute solution.     

Relationship of temperature to composition of copolymers of α-methylstyrene and maleic anhydride

Alternating copolymers of α-methylstyrene and maleic anhydride were prepared in good yields in a decalin solution at temperatures below 80°C. Random copolymers with large percentages of α-methylstyrene were obtained in good yields at higher temperatures. These results were in accord with the charge transfer complex which was characterized by n.m.r. and u.v. spectrophotometry and shown to exist below 80°C. The copolymers were characterized by pyrolysis/gas chromatography and differential scanning calorimetry. The glass transition temperature of poly(α-methylstyrene) and the random copolymer of this monomer and maleic anhydride were approximately 450 and 458 K respectively.     

Synthesis and properties of novel random and block copolymers composed of phthalimidine‐ and perfluoroisopropylidene‐polyarylether‐sulfones

A series of novel polyarylethersulfone (AB) _n block copolymers with different segment lengths have been synthesized by nucleophilic solution polycondensation of phenoxide‐terminated and fluorine‐terminated oligomers; random copolymers have been prepared over the whole composition ranges. The structures of the resultant copolymers have been confirmed by FTIR, ¹³C NMR spectra and differential scanning calorimetry (DSC). Compared with two homopolymers and random copolymers, the block copolymers of this study possess excellent thermal stability (5% thermal decomposition under nitrogen atmosphere above 500 °C) and high glass transition temperatures, and have a wide melt‐processing temperature range. They may become a new class of mouldable high performance thermoplastics. © 2001 Society of Chemical Industry     

Determination of unsaturation in ethylene-propylene terpolymers and butyl rubber by time-averaged 1H n.m.r. measurements

The time-averaged ¹H n.m.r. spectra of ethylene-propylene-dicyclopentadiene, ethylene-propylene-ethylidene norbornene and isobutylene-isoprene copolymers were measured. Assignments of the olefinic resonances were carried out by comparing the spectra with those of each homopolymer and strarting monomers. The concentration of the olefinic unit in copolymer was determined by measuring the intensity ratio between the olefinic proton signal and the signal of trichloroethylene which was added as an internal standard of intensity measurements. The concentrations of unsaturation in copolymers determined by using the iodine-mercuric acetate method were proportional to those determined by the n.m.r. method. The accuracy and precision of the n.m.r. measurements were shown to be better than 10% for a mixture of polyisobutylene and polyisoprene containing 1.24 mol % of unsaturation as a model compound of isobutylene-isoprene copolymer.     

Synthesis and characterization of α‐amino acid‐containing polyester: poly[(ε‐caprolactone)‐co‐(serine lactone)]

Novel polyesters, poly[(ε‐caprolactone)‐co‐(N‐trityl‐L ‐serine‐β‐lactone)]s, were prepared by copolymerizing ε‐caprolactone (CL) with N‐trityl‐L ‐serine‐β‐lactone (TSL) using ZnEt₂ as the catalyst. The number‐average molecular weights were determined which ranged from 2.7 × 10⁴ to 4.9 × 10⁴ Da with dispersity values ranging from 1.6 to 1.8. The structures of the copolymers were investigated by means of ¹H NMR, ¹³C NMR and infrared spectroscopies, thermogravimetric analysis and differential scanning calorimetry. The results indicated that CL and TSL monomer units were randomly distributed within the copolymer backbone structures and the ratios of TSL to CL in the copolymers were close to those in the feeds. After removal of the trityl group under mild condition, a new polyester with side amino groups provided by serine units was obtained. L929 cell culturing test indicated good biocompatibility of the polyester with or without protective groups. © 2012 Society of Chemical Industry     

Recovery,fractionation and study of oils from a lignite

Oils from a lignite (Teruel, Spain) were studied. They were obtained by catalytic depolymerization, by reacting an aromatic substrate (tetralin), Lewis acid catalyst (BF₃) and the lignite (oil A) or asphaltenes (oil B) at atmospheric pressure and temperatures <220 °C. The A and B oils were fractionated on an alumina-silica gel dual column into their saturated, mono- and diaromatic, polyaromatic and polar components by elution with hexane, hexane-benzene, benzene and methanol-diethyl ether-benzene respectively. The elemental analysis, average molecular weight, i.r. and ¹H n.m.r. spectroscopy and aromaticity data of these subfractions were studied.     

The copolymerization of methyl methacrylate and isoprene in the presence of ethyl aluminium sesquichloride: role of monomer complexes

The kinetics of the spontaneous copolymerization of methyl methacrylate and isoprene in the presence of ethyl aluminium sesquichloride in toluene and at temperatures between 0° and 40°C have been investigated. Irreproducible fast initial rates of copolymerization are followed by slower reproducible rates. The structures of the copolymer and the accompanying Diels-Alder adduct have been determined by ¹H and ¹³C n.m.r.; the copolymers produced under a wide range of conditions are equimolar and highly alternating. The concentrations of various binary and ternary complexes have been assessed through ¹H n.m.r. chemical shift measurements; it is shown that the mechanism of copolymerization cannot involve simply the effective homopolymerization of ternary isoprene-methyl methacrylate-ethyl aluminium sesquichloride complexes.     

Short chain branching in high density polyethylene: 13C n.m.r. study

The character and amount of branching has been determined by ¹³C. n.m.r. spectroscopy, in a series of samples of high density polyethylene (HDPE) and in some ethylene copolymers of high density. HDPE samples prepared by different methods were studied and only methyl branches were found; however, the number of branches differs considerably in various polymers. The quantitative determination of the branches is in good agreement with the results of infra-red spectroscopy. The relation between the type of branches and the crystallinity of polyethylene is discussed.     

Aggregation behaviour of stereoregular poly(methyl methacrylates) in dilute solution: light scattering and proton n.m.r. study

The aggregation behaviour of syndiotactic and isotactic poly(methyl methacrylate) in methyl ethyl ketone, n-butyl acetate, and 2-ethoxyethanol was investigated by light scattering and ¹H n.m.r. spectroscopy. Syndiotactic poly(methyl methacrylate) remains in its molecular form in solution at temperatures above 60°–70°C; on cooling it undergoes aggregation followed by macroscopic separation (precipitation) of the polymer from solution. The rate of these processes depends on temperature, concentration of the polymer, and solvent. Molecular solutions of isotactic poly(methyl methacrylate) can be prepared only by long-term heating at temperatures above 100°–130°C. During cooling, isotactic macromolecules prior to separation form stable associates in the region limited by discrete temperatures, and below this region polymer precipitates. The individual stereo forms of poly(methyl methacrylate) are separated from solution at different temperatures which are above the θ-temperatures of the atactic polymer.     

The tacticity of poly(tri-n-butyl tin methacrylate) determined by 13C n.m.r.

The tacticities of poly(tri-n-butyl tin methacrylate)s prepared with radical initiators at various temperatures have been measured by ¹³C n.m.r. As expected, the polymers are predominantly syndiotactic and this syndiotacticity decreases with an increase in temperature. The activation parameters governing the tacticity are similar to those published for poly(methyl methacrylate) but differ somewhat from values published for poly(trimethyl tin methacrylate).