Derivative infrared spectroscopy of cotton cellulose

A new technique of derivative infrared spectroscopy for the study of polymer structure with special reference to cotton cellulose is described. Absorption spectra of cotton cellulose are compared with second deravative spectra. In case of absorption spectra, while determining the wavelength and intensity of a given absorption, in many cases, difficulties arise due to the presence of an interfering band which, as a consequence of overlap, prevents the determination of the above properties. Derivative spectroscopy provides valuable information on structural properties of cellulose. It yields spectra gradient, which facilitates the separation of overlapping absorption bands to resolve and detect absorptions; neither were unresolvable as a consequence either of multiple bands overlap or of low intensity. Hence, the measured wavelength in the second derivative spectra are more precise than the absorption spectra. For fine structural studies of cellulose, derivative spectra may provide more useful information as the absorption bands are more clearly defined.     

Preparation and properties of poly(Nε,Nε-dicarboxymethyl-l-lysine)

A new ampholytic homopolypeptide, $\text{poly}\text{(N}{}^{\mathrm{\epsilon }}\text{,N}{}^{\mathrm{\epsilon }}\text{-}\text{dicarboxy-methyl-}\text{l}\text{-lysine}\text{)}$, which has one tertiary amino and two carboxyl groups in the side chain has been derived from a hydrochloride salt of poly(L-lysine). The polymer in aqueous solution seems to be in the coil form with locally extended structure (LES) at neutral pH. In both the acidic and alkaline regions, the molar ellipticity of the polymer changes as a result of change in net charge on the side chain. The conformational changes may be from the coil with LES to other coiled forms. 5–7 M NaClO₄ and 80% aqueous methanol induce the α-helix in the polymer at neutral pH. Divalent cations, Cu²⁺ and Ca²⁺, do not induce any remarkably ordered structures such as α-helix or β-structure in the polymer in aqueous solution at any pH. Ultraviolet absorption studies show an absorption peak of the polymer-Cu²⁺ complex near 240 nm. Dependence of the peak intensity on pH at various q values ($\text{q =}\text{[}\text{Cu}{}^{\mathrm{2+}}\text{]}\text{[}\text{residue}\text{]}$) indicates the two steps of the complex formation. At q less than 0.64, the formation is described only with the first step. An average coordination number for Cu²⁺ at the first step was calculated to be about 2 by the method of Mandel and Leyte. The association constant of Cu²⁺ with the residue at the step was determined from the absorption data to be far smaller than that for the Cu²⁺-EDTA complex. The second step of the formation occurs in the case of large q but the absorption data for the second step cannot be obtained exactly due to precipitation.     

Crystallographic changes characterizing the Curie transition in three ferroelectric copolymers of vinylidene fluoride and trifluoroethylene: 2. Oriented or poled samples

The effects of uniaxial drawing or poling on the structural changes involved in the ferroelectric-to-paraelectric phase transition in copolymers of vinylidene fluoride and trifluoroethylene were examined and compared to the behaviour of as-crystallized films. The compositions studied were $\text{65}\text{35}$, $\text{73}\text{27}$ and $\text{78}\text{22}\text{mol}\text{\%}$ vinylidene fluoride/trifluoroethylene, all of which crystallize from the melt with a molecular conformation and packing analogous to those of the common piezoelectric β-phase of poly(vinylidene fluoride). Contrary to the previously described behaviour of a $\text{52}\text{48}\text{mol}\text{\%}$ copolymer, orientation did not induce any significant changes in the structure of these copolymers or in its variation with temperature, primarily because these already crystallize directly from the melt in well-ordered, compact unit cells. On the other hand, electrical poling caused the all-trans chains of the ferroelectric phase to be packed more compactly and to survive to higher temperatures, thus shifting the Curie transition closer to the melting points of these copolymers. As a result, competition from melting interfered with the later stages of this solid-state transformation in the $\text{73}\text{27}\text{mol}\text{\%}$ composition, and aborted it at a very early point in the $\text{78}\text{22}\text{mol}\text{\%}$ samples. The Curie temperature was found to exhibit hysteresis between heating and cooling parts of the thermal cycle, to extend over a broad range of temperatures, and to involve intramolecular changes to the same disordered conformation found in melt-crystallized samples. Our results have allowed reasonable implications to be made concerning the existence and nature of a Curie transition in the piezoelectric β-phase of poly(vinylidene fluoride).     

Structure of polystyrene glasses

Wide-angle X-ray scattering from both unoriented and axially deformed glassy polystyrenes (atactic and quenched isotactic) is compared with that calculated for isolated molecules in different conformations. No satisfactory fit is obtained. It is apparent that the scattering beyond $\text{s=1.0}\text{A}\text{?}{}^{\mathrm{?1}}$ is very similar to that from benzene and styrene, having a large contribution from contacts between phenyl groups attached to neighbouring molecules which are not represented in a single chain model. The only significant difference between the scattering of the polymer and the two low molecular weight liquids is that there is a small peak at $\text{s=0.75}\text{A}\text{?}{}^{\mathrm{?1}}$ (0.62 Å^?1 for the isotactic glass) which forms on polymerization and was first reported by Katz in 1927. For drawn samples the peak intensifies on the equator and apparently represents interchain correlations. However, in comparison with those of other non-crystalline polymers this interchain peak is weak, at a surprisingly low scattering angle in relation to the expected spacing of the chains and shows a very significant increase in intensity with increasing temperature. A model is proposed in which the phenyl groups segregate on a molecular scale to form stacks; there are fewer stacks than chain backbones and they have a low electron density core which expands considerably in relation to its small diameter as the sample temperature increases. The model accounts for the position and temperature sensitivity of the interchain ‘polymerization’ peak. It also shows some similarities to the organization of isotactic molecules in the crystalline state. The stacks of phenyl groups contribute to the X-ray pattern as if they were flexible superchains. The cylindrical distribution function derived from the scattering pattern of the oriented polymer indicates that the phenyl groups are in register in all directions over distances of the order of several chain diameters.     

Low frequency excitation in amorphous acrylic polymers

Low frequency Raman depolarized spectra from poly(methyl methacrylate) have been determined at temperatures between 293 K and 85 K in the frequency region $\text{5}\text{cm}{}^{\mathrm{?1}}\text{<}\text{v}\text{?}\text{<2000}\text{cm}{}^{\mathrm{?1}}$. All the reduced intensity spectra resolve into two bands: a broad and intense band at 91 cm^?1 and a narrower and weaker band at 22 cm^?1. The Raman intensities do not depend on temperature which implies first order Raman scattering. Room temperature low frequency Raman spectra were also recorded from poly(ethyl methacrylate) and poly(-n-butyl methacrylate). In the two PMMA substitutes the high frequency band is shifted to lower values as the side group mass is increased and show a Debye-like character. The lower frequency band cannot be resolved in the spectrum of PEMA and PnBMA. The two bands at 91 cm^?1 and 22 cm^?1 are attributed to side group and backbone motions respectively. By studying PMMA samples of different tacticity no dependence of the band frequency on chain configuration has been detected. The density of states g(Ω) obtained through the low frequency Raman spectrum has been used to calculate the specific heat C_v. The values of C_v obtained are lower than those measured calorimetrically but varied with temperature in a similar manner in the region 0.8<T<4K.     

Poly(ethyleneoxide-b-styrene) copolymers as solid—liquid phase transfer catalysts

Di- and tri-block copolymers of ethylene oxide and styrene function as effective phase transfer catalysts in the reaction of solid potassium phenoxide with n-butylbromide in refluxing toluene to give virtually quantitative yields of n-butyl phenyl ether. A wide range of copolymer structures have been examined and the catalytic activity is found to increase with $\text{M}\text{?}{}_{\mathrm{n}}$ of both the styrene and the ethylene oxide segments levelling off at $\text{M}\text{?}{}_{\mathrm{n}}$ styrene block ～30 000 and $\text{M}\text{?}{}_{\mathrm{n}}$ ethylene oxide block ～60 000. Beyond $\text{M}\text{?}{}_{\mathrm{n}}$ ethylene oxide block ～100 000 rates of reaction drop again towards the value for a high molecular weight homopolymer of ethylene oxide. Kinetic analysis suggests the rate controlling process to be the bimolecular reaction between complexed potassium phenoxide and n-butyl bromide, and the activation energy for the reaction is the same as that for reactions catalysed by low molecular weight oligoethers. From the kinetic dependence of the concentration of copolymer catalysts, the dependence on the structure of individual copolymers and from the known physical behaviour of these copolymers in toluene solution, catalysis appears to involve micellar aggregates of copolymer chains.     

Self-assembly of novel tris(p-carboxyphenyl) porphyrin monomer and its copolymers with acrylamide in aqueous media

The novel porphyrin monomer 5-(4-acryloyloxylphenyl)-10,15,20-tris(4-carboxyphenyl)porphyrinate zinc(II) (ZnAOTCPP) and its corresponding sodium salt (ZnAOTCPP-Na) were synthesized. The latter compound exhibited a new band in excitation spectra due to formation of porphyrin aggregates in water, which were derived from its surface-activity when the concentration was higher than its critical association concentration (CAC). The porphyrins were copolymerized with acrylamide (AM) to prepare water-soluble copolymers with random and micro-blocky structures, which all displayed very new absorption and fluorescence emission bands in the long wavelength region compared with the porphyrin monomer. Furthermore, the micro-blocky copolymer exhibited an additional new absorption band at even longer wavelength region compared with the random copolymer. The experimental results and analysis showed that the porphyrin units in the random copolymer chains self-assembled to form porphyrin association complexes by hydrophobic association and π-π stacking interactions, and covalent restrictions of polymer chains in the micro-blocky copolymer.     

Thermal decomposition of a vinyl chloride/vinyl acetate copolymer

The thermal decomposition of an 85% vinyl $\text{chloride}\text{15\%}$ vinyl acetate copolymer and its different fractions obtained by precipitation was studied by the thermogravimetric scanning (t.g.s.) technique. Analyses of the t.g.s. thermograms revealed the existence of two major steps in the decomposition reaction. The first occurs between 180 and 380°C during which hydrogen chloride and hydrogen acetate are given off. In the second, which occurs between 420 and 480°C, degradation of the carbon chain takes place. Both the order of reaction and the activation energy were found to be dependent on the molecular weight of the copolymer and on the heating rate at which the experiments were carried out. Analyses of the samples carried out by gel permeation chromatography (g.p.c.) after each decomposition revealed that, besides the two steps mentioned above, yet another step, viz. crosslinking, may be taking place at 180°C or below where the weight loss of copolymer is too small to be detected by t.g.s. The process of crosslinking, however, may take place at other temperatures as well. A higher degree of crosslinking has been associated with a higher acetate content in the copolymer. A comparison of g.p.c. results with those obtained by nuclear magnetic resonance spectra showed that, out of the three steric configurations of the copolymer, syndiotactic sequences are least resistant to thermal treatment followed in order by heterotactic and isotactic sequences.     

Low frequency excitations in amorphous polycarbonate studied by Raman spectroscopy

Low frequency excitations in amorphous polycarbonate-bisphenol A have been studied by Iaser Raman spectroscopy in the frequency region $\text{5}\text{cm}{}^{\mathrm{?1}}\text{< Δ}\text{v}\text{?}\text{< 200}\text{cm}{}^{\mathrm{?1}}$. Depolarized spectra were recorded at temperatures between ambient and 85 K, the reduced intensity spectra show no temperature dependence. Two bands are resolved in the reduced intensity spectrum: a strong band around 96 cm^?1 and a weak band around 45 cm^?1; these are attributed to the effects of longitudinal and transverse phonon waves originating in backbone motion. The low frequency Raman intensities provide information on the density of state g(ω) from which the specific heat, C_v, of polycarbonate has been calculated. This is found to vary with temperature in a manner similar to the calorimetrically measured C_v in the low temperature range ～1 K < T < 4 K.     

Crystallographic changes characterizing the Curie transition in three ferroelectric copolymers of vinylidene fluoride and trifluoroethylene: 1. As-crystallized samples

Copolymers of vinylidene fluoride/trifluoroethylene of molar composition $\text{65}\text{35}$, $\text{73}\text{27}$ and $\text{78}\text{22\%}$ respectively, are ferroelectric and undergo a Curie transition to the paraelectric state at high temperatures. In contrast to the irregular structure found earlier for the $\text{52}\text{48}\text{mol}\text{\%}$ copolymer, the structures of these three compositions in the low-temperature state are all well ordered and analogous to that of β-poly(vinylidene fluoride): they consist of molecular chains in a polar trans conformation whose order is improved with increasing vinylidene fluoride content, packed pseudo-hexagonally in unit cells whose dimensions decrease with increasing vinylidene fluoride content. In their paraelectric phase, the chains assume a partly disordered conformation consisting of irregular TG, T? and TT sequences and are packed on an expanded pseudo-hexagonal lattice. The Curie transitions were found to occur over a broad temperature range, encompassing ～30°C, and in the case of the $\text{78}\text{22}\text{mol}\text{\%}$ copolymer to extend into the melting region; they were also found to exhibit hysteresis by occurring at much lower temperatures upon cooling than upon heating.     

Synthesis and conformation studies of copolypeptides composed of γ-methyl-l-glutamate and ε-N-carbobenzyloxy-l-lysine

Copolypeptides (PMGCL) composed of γ-methyl-l-glutamate(MLG) and $\text{?-N-}\text{carbobenzyloxy-}\text{l}\text{-lysine(CBL)}$ covering the whole range of copolymer composition were synthesized by the N-carboxyanhydride (NCA) method. The experimentally obtained monomer reactivity ratios were r₁(MLG)=2·0±0·4 and r₂(CBL)=0·5±0·1, from which the fractions of monomer dyads and triads in copolymer were plotted against the initial comonomer composition. From experimental results on thermally induced coil-to-helix transition of the copolypeptides in dichloroacetic acid/1,2-dichloroethane (DCA-DCE) systems, it has been found that these copolypeptides can exist in the α-helix conformation in the same manner as homopolypeptides PMLG and PCBL. The van't Hoff heat of transition ΔH showed a minimum against the initial monomer composition. The enthalpy ΔH_res of formation of intramolecular hydrogen bonds per peptide bond also showed a minimum against copolymer composition. Such behaviour on ΔH and ΔH_res was also found for copolypeptide (PBGCL) composed of γ-benzyl-l-glutamate(BLG) and $\text{?-N-}\text{carbobenzyloxy-}\text{l}\text{-lysine(CBL)}$ in DCA-DCE systems reported in a previous paper. The presence of a minimum in these relationships may be attributed to specific interactions between the side chain of one comonomer and that of the other comonomer in a two component copolymer. It is also pointed out that these copolymer molecules can exist in the α-helix conformation in the solid state.     

UV absorption spectra of polystyrene

Summary Polystyrene (PSt) exhibits a new UV absorption band at around 290nm in comparison with ethylbenzene, which is attributed to associative interaction between pendant phenyl groups. Similar absorption bands are also observed for polymers of styrene derivatives. The UV spectra suggest charge-transfer complex formation between the polymeric and monomeric donors with electron-acceptor tetracyanoethylene (TCNE) and the equilibrium constants were estimated to be in the sequence of ethylbenzene > PSt > copolymer of St with methylmethacrylate.     

Shielding Behavior of Gamma-Irradiated MoO<Subscript>3</Subscript> or WO<Subscript>3</Subscript>-Doped Lead Phosphate Glasses Assessed by Optical and FT Infrared Absorption Spectral Measurements

Undoped and MoO₃- or WO₃- doped lead phosphate glasses were prepared by the melting-annealing technique. The glasses were characterized through UV-visible and infrared measurements which were repeated after gamma irradiation. Optical spectrum of binary lead phosphate glass shows distinct ultraviolet bands correlated with unavoidable trace iron impurities within the chemicals used for the preparation of the glasses. UV-visible absorption spectra of MoO₃- or WO₃- doped glasses exhibit additional UV-visible bands which are related to the presence of four oxidation states of the two transition metal (molybdenum or tungsten) ions (Mo³⁺, Mo⁴⁺, Mo⁵⁺, Mo⁶⁺, W³⁺, W⁴⁺, W⁵⁺, W⁶⁺). The extra UV band is related to hexavalent (5d⁰) state while the rest of the visible bands are related to (350–440 nm - trivalent state), (450, 550, 650 nm - tetravalent state) while the broad band centered at about 770 nm (pentavalent state). The intensities of the absorption bands are observed to change with the transition metal content and their valencies. Infrared absorption spectra reveal distinct vibrational bands which are assigned to phosphate groups with sharing of Pb-O vibrations within both the range 460–620 cm^-1 and the range 900–1100 cm^-1 revealing a compact network structure. Gamma irradiation causes a minor increase in intensity of one of the UV band due to suggested photo-oxidation of some trace ferrous ions to additional ferric ions but the remaining spectral curve remains unaffected which is obviously related to some shielding effects of heavy atomic weight of PbO. This heavy metal oxide (PbO) is assumed to retard or prohibit the free passage of free electrons or positive holes generated during the irradiation process.     

Conformational study of the sequential (Tyr-Glu)n copolymer in aqueous solution

Conformational properties of the sequential poly(Tyr-Glu) copolymer in aqueous solution were investigated as a function of pH. No transition could be detected over the range pH 13-10.5. Below pH 10.5 an aggregation process takes place, causing a drastic change in all optical properties of the polymer (optical rotation, c.d. and u.v. spectra). By means of i.r. spectroscopy in D₂O, aggregates were found to be in antiparallel β conformation. The c.d. spectrum of β-aggregates is very similar to that of α-helical poly(l-tyrosine) in organic solvents, except in the 280 nm region. In addition the aggregation process is accompanied by a strong hyperchromic effect in the 277 nm absorption band. Using space-filling models, different arrangements of the chains in the β-aggregates were shown to be realizable. All result in a close stacking of tyrosyl phenyl groups, which can explain the drastic changes in all optical properties.     

Investigation of the methyl torsion in isotactic polypropylene — comparison between neutron inelastic scattering spectra and normal coordinate calculations

Incoherent neutron scattering spectra for polypropylene and its partially deuterated analogue allow identification of the methyl torsion at 230 cm^?1. Comparison of the experimental spectra with the calculated densities of states shows discrepancies with the expected intensity of the methyl torsional band. Results from a stretch-oriented sample arranged so that the wave vector $\text{Q}$ is first parallel ($\text{Q}{}^{\mathrm{\parallel }}$) and then perpendicular ($\text{Q}{}^{\mathrm{\perp }}$) to the helical chain axis indicate that the torsion is more intense and probably has a small frequency dispersion around 240 cm^?1 for $\text{Q}{}^{\mathrm{\parallel }}$ and is weaker with a broad dispersion centred at 220 cm^?1 for $\text{Q}{}^{\mathrm{\perp }}$.     

Characterization of polyazomethines in dilute solution. Correlation between the light scattering parameters and the u.v.-visible absorption spectrum

The high values 1 (up to cm³ g^?1) of the refractive index increments $\text{d}\text{n}\text{d}\text{c}$ of sulphuric and methane sulphonic acid solutions for a series of polyazomethine compounds at 546 and 628 nm are related quantitatively to the existence of a strong absorption band around 400 nm. The frequency dependence is well explained by the anomalous dispersion calculated from the decomposition of the absorption band into Gaussians. The blue shift and hypochromic effect, and the correlated decrease in $\text{d}\text{n}\text{d}\text{c}$, resulting from an aggregation process in methane sulphonic acid can be interpreted by a side-by-side arrangement of aggregates. This result is substantiated by a calculation of the optical anisotropy from the depolarized part of the scattered light.     

N.m.r. of random copolymers of benzyl-l-aspartate with o- and p-nitrobenzyl-l-aspartate

The p- and o-substitution of the benzene ring of poly(β-benzyl-l-aspartate) (PBLA) with a nitro group induces a reversal of the helix sense in the PBLA. Therefore, two series of random copolymers of benzyl-l-aspartate with o- and p-nitrobenzyl-^l-aspartate were prepared in order to study the left-handed→right-handed α-helix transition. The conformational behaviour has been studied by nuclear magnetic resonance spectroscopy and the left-handed→right-handed α-helix transition has been observed from the α-CH shift, from CDCl₃ solutions. Moreover, for each copolymer, the α-helix→coil transition was also studied in $\text{CDCl}{}_3\text{trifluoroacetic acid}$ mixtures. In this case, the transition can be observed from the α-CH shift and from the splitting of the β-CH₂ resonance in the α-helical form also.     

Fourier transform infra-red spectroscopy of nylon-6 blends: binary blends with poly(methyl methacrylate) and ethylene vinyl ester/alcohol copolymer

Films of blends of nylon-6 with poly(methyl methacrylate), (PMMA) and poly(ethylene-vinyl alcohol) were cast from formic acid solutions and examined by Fourier transform infra-red spectroscopy. At high contents of nylon-6 the vinyl alcohol of the copolymer reacts with formic acid to form vinyl formate. In contrast, the films of 100% copolymer and of the $\text{25}\text{75}$ and $\text{10}\text{90}$ blends contained both the alcohol and the ester groups. The FTi.r. results indicate that there are specific interactions between the amide group on nylon-6 and the ester group of PMMA or the copolymer. Data are also presented which show that there are at least two amorphous phases - one miscible containing both the polymers and the other containing almost pure noncrystallizable component. The differences in the specific interactions in the two blend systems are largely due to the inversion of the ester group in the pendant chain.     

Syntheses and properties of tetramethyl-p-silphenylenesiloxanealkenylmethyl-siloxane copolymers and their derivatives

$\text{Tetramethyl}\text{-p-}\text{silphenylenesiloxane}\text{alkenylmethylsiloxane}$ (TMPS/AMS) copolymers were snyhtesized from p-bis-dimethylhydroxysilylbenzene and a series of alkenylmethyldichlorosilanes as the starting materials. The alkenyl groups of the copolymers were vinyl, allyl, 2-(3-cyclohexenyl)ethyl, methacryloxypropyl and 3-bicycloheptenyl groups. The composition ranged from TMPS/AMS mole% ratio of $\text{92}\text{8}$ to $\text{83}\text{17}$ and the molecular weights were in the range 10⁴ to 10⁵. These copolymers were confirmed to have two compositions, one a certain length of TMPS segment and the other an AMS monomer unit, and that they could form films on the basis of the crystallization character of the TMPS segment. The melting temperatures of these copolymers decreased as the TMPS mole content decreased and as the alkenyl group contents were increased. The epoxidation reactions of these copolymers with m-chloroperbenzoic acid were carried out and the proportions of conversions of the alkenyl groups into epoxy groups varied depending upon the types of alkenyl groups involved. Cyclic olefin groups such as the 2-(3-cyclohexenyl)ethyl or the 3-bicycloheptenyl group were more easily epoxidized than the vinyl or allyl groups. The TMPS/dimethylsiloxane (DMS) graft copolymer could also be synthesized by the reaction of TMPS/vinylmethylsiloxane copolymer with dimethylhydrosilyl-terminated DMS oligomer in the presence of chloroplatinic acid acting as the catalyst.     

Synthesis,electronic spectra and solvatochromic behaviour of 4-arylidene-1-(2,4-dinitrophenyl)-3-methyl-2-Pyrazolin-5-ones

The u.v.-visible electronic spectra of 4-arylidene-1-(2, 4-dinitrophenyl)-3-methyl-2-pyrazolin-5-ones ( 1a-f ) have been studied. The different bands observed have been assigned to the proper electronic transition. Solvatochromic behaviour of these compounds is investigated by studying their visible spectra in organic solvents of different polarity. The longer wavelength band displayed by the hydroxy derivatives is assigned to an intermolecular CT transition. The H-bonding solvated complexes formed between ethanol or DMF and p-hydroxy substituted derivative are investigated. Transition moment (μCT), ΔG and K_f values of these complexes have been determined.