Distribution of isomeric structures in polyisoprenes

The ¹³C-n.m.r. spectra of polyisoprenes were investigated. Polyisoprenes were prepared with $\text{n-Buli}\text{Et}{}_2\text{O}$, radical (emulsion polymerization), and Alfin catalysts. Poly(isoprene-4,4-d₂)s were also prepared with $\text{n-BuLi}\text{Et}{}_2\text{O}$ catalysts for the signal assignments. ¹³C-n.m.r. signals were assigned for dyad or triad sequences of cis-1,4-, trans-1,4-, and 3,4- units. Signals due to head-to-head (4,1-1,4) and tail-to-tail (1,4-4,1) linkages were also assigned. On the basis of signal assignments it was revealed that cis-1,4-, trans-1,4-, and 3,4-units were distributed almost randomly in $\text{n-BuLi}\text{Et}{}_2\text{O}$ catalysed polyisoprenes. It was confirmed that radical and Alfin polyisoprenes contained about 15% of each of head-to-head and tail-to-tail linkages. It was found that radical polyisoprene had cis-1,4- and trans-1,4-units distributed randomly along the polymer chain regardless of the head and tail arrangements.     

Random-coil configurations of alicyclic polyformals

A sample of poly (trans-1,4-cyclohexylene-dimethylene-oxymethylene oxide) (PTCDM) was synthesized by condensation of trans-1,4-cyclohexane dimethanol and paraformaldehyde using p-toluene sulphonic acid as catalyst. A fraction having M_n=6500 and a melting point of 86°C was isolated and purified; its n.m.r. spectrum does not change with temperature in the range 20°–50°C which indicates a rigid distribution of methylene substituents in the cyclohexane ring; its dipole moment, measured in benzene solution at several temperatures between 20° and 60°C, yielded values of $\text{D}{}_{\mathrm{n}}\text{=}\text{[μ}{}^2\text{]}\text{nm}{}^2\text{=0.17–0.21}$ and a temperature coefficient dln $\text{{gm}{}^2\text{}}\text{d}\text{T}\text{= 5.5 × 10}{}^{\mathrm{?3}}\text{K}{}^{\mathrm{?1}}$, similar to those reported in the literature for acyclic polyformals. Agreement between experimental and calculated (using rotational isomeric states theory) values is satisfactory.     

Solution properties and chain flexibility of polythiolmethacrylates: 1. Poly(phenyl thiolmethacrylate) and poly(O-methyl phenyl thiolmethacrylate)

Dilute solution properties of poly(phenyl thiolmethacrylate) (PTPh) and poly(o-methylphenyl-thiolmethacrylate) (PTMPh) were studied by gel permeation chromatography, light scattering, osmotic pressure and viscosity measurements in different solvents. Relations between intrinsic viscosity [η], z-average root-mean-square end-to-end distance $\text{(}\text{r}\text{?}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and molecular weight $\text{M}\text{?}{}_{\mathrm{w}}$ were established. The unperturbed dimensions were calculated by different methods using $\text{M}\text{?}{}_{\mathrm{w}}$ and [η]. PTPh (σ = 2.26) and PTMPh (σ = 2.27) have practically the same flexibility, but both are more flexible than poly(phenyl methacrylate) (σ = 2.50). In our opinion, this is due to the change in the local intramolecular interaction and the higher flexibility of the sulphur-containing side group.     

Polyacrylamide in water: molecular weight dependence of 〈R2〉 and [η] and the problem of the excluded volume exponent

A commercial sample of polyacrylamide (CALGON) has been carefully purified, analysed and fractionated. With suitable care, the molecular characterization can be carried out by light scattering and viscosity measurements, without disturbances arising from microgels or aggregates. The molecular weight dependence of the radius of gyration and intrinsic viscosity are given by:

$\text{〈R}{}^2\text{〉}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 7.49 × 10}{}^{\mathrm{?}}\text{M}{}^{0.64}\text{(}\text{A}\text{?}\text{)}$

$\text{[η] = 9.33 × 10}{}^{\mathrm{?3}}\text{M}{}^{0.75}\text{(cm}{}^3\text{/g)}$

The value of the exponent ν = 0.64 in the $\text{〈R}{}^2\text{〉}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ equation has been cross-checked by a study of the asymptotic behaviour of the scattering envelope. Such a value is higher than that expected in a good solvent (ν = 0.60) and should lead to a higher exponent in the intrinsic viscosity dependence. However, it agrees more closely with the published dependence of sedimentation and diffusion coefficients.     

Phosphonitrilic chloride: 34. Electrical conductivity of polybisaminophosphazenes

The electrical conductivity of polybisaminophosphazenes investigated over a range of temperatures was found to obey the general relation for semi-conductors. The resistivity decreased or increased when a side group having a high inductive effect or bulky group was linked in the polymers. The electrical conductivity of polybisaminophosphazenes containing primary amine, secondary amine and aromatic amine ranged from 1.3 × 10¹⁰ to $\text{2.8 × 10}{}^{10}\text{Ω-}\text{cm}$, 9.3 × 10¹⁰ to $\text{8.5 × 10}{}^{11}\text{Ω-}\text{cm}$ and above $\text{9.1 × 10}{}^{14}\text{Ω-}\text{cm}$, respectively.     

Rigid backbone polymers, XVII: Solution viscosity of polydisperse systems

When plotted against concentration V⁰₂, the viscosity η⁰ curve of isotropic solutions of lyotropic nematic mesomorphic polymers increases according to:

$\text{η}{}^0\text{=η}{}_0\text{[[η]V}{}^0{}_2\text{+(}\text{π}\text{4}\text{)[η]}{}^2\text{(V}{}^0{}_2\text{)}{}^2\text{+K}{}_2\text{(}\text{ln}\text{x}\text{)}{}^2\text{[η]}{}^3\text{(V}{}^0{}_2\text{)}{}^3\text{+…]}$

in which η₀ is the solvent viscosity, K₂ a numerical constant, x? is the average molecular axial ratio and [η] the intrinsic viscosity as defined by:

$\text{[η]=}\text{2}\text{x}{}^2\text{45}\text{1}\text{ln}\text{2}\text{x}\text{?1.84}\text{+}\text{3}\text{ln}\text{2}\text{x}\text{?0.61}\text{(+}\text{14}\text{15}\text{)}$

At the concentration $\text{v1}{}_2$ an anisotropic phase appears and the viscosity curve shows a decrease in slope followed by a change in direction at a peak viscosity η^p at v^p₂. Upon further increase in v⁰₂ the system undergoes a phase inversion and finally turns fully anisotropic at v^A₂. In the biphasic interval the viscosity is described by:

$\text{η}{}^0\text{=η}{}_{\mathrm{<mtext>mat</mtext>}}\text{1+}\text{(5λ+2)}\text{2(λ+1)}\text{V}{}_{\mathrm{<mtext>inc</mtext>}}$

where $\text{λ =}\text{η}{}_{\mathrm{<mtext>inc</mtext>}}\text{η}{}_{\mathrm{<mtext>mat</mtext>}}$, the ratio of the inclusions viscosity to the matrix viscosity, and v_inc the volume fraction of the inclusions in the system. It must be emphasized that the molecular weight of the polymer in both phases changes continuously with concentration, resulting in commensurate changes in η_ince, η_mat and their ratio λ. In the anisotropic region the viscosity first decreases moderately and then increases precipitously with v⁰₂, according to:

$\text{η}{}^0\text{=η}{}_0\text{[}\text{2}\text{x}{}^2\text{90S}\text{(}\text{5}\text{ln}\text{2}\text{x}\text{?1.8}\text{+}\text{6}\text{ln}\text{2}\text{x}\text{?0.61}\text{)+2]}\text{V}{}^0{}_2\text{1-}\text{V}{}_{\mathrm{25°}}\text{V}{}_{\mathrm{E}}$

in which S is an order parameter and V₂₅, V_E are volumes swept by the orbits of the flowing rodlike macromolecules. The equations give results in good qualitative and fair quantitative agreement with experimental data in the literature.     

Conformational studies of N-acetyl-N-methyl-l-alanine dimethylamide-d6 by n.m.r. spectroscopy

Nuclear magnetic resonance of $\text{N-}\text{acetyl}\text{-N-}\text{methyl-}\text{l}\text{-alanine dimethylamide-d}{}_6$ in methylene $\text{chloride}\text{-d}{}_2\text{dichloroacetic acid}$ was investigated. In methylene chloride-d₂ the amide assumed nearly all-trans conformation. Small signals corresponding to trace amounts of cis confirmation were observed. Dichloroacetic acid induced the shift of the resonance signals immediately after the addition. On leaving the solution containing dichloroacetic acid, the amide nitrogen was protonated and the isomerization around the amide bond took place. After a sufficient time lapse a complex spectrum resulted, which corresponded to at least five different conformations. On heating the solution several signals disappeared without coalescence and the resonance signals corresponding to three different conformations remained at 120°C. These conformations should include non-planar conformations as well as planar cis and trans conformations.     

Characterization of poly(1,4-phenyleneterephthalamide) in concentrated sulphuric acid: 1. Static and dynamic properties

Laser light scattering including angular dependence of total integrated scattered intensity and of the spectral distribution has been used to characterize five samples of poly(1,4-phenylene terephthalamide), PPTA (commercially known as Kevlar), of different molecular weights in 96% sulphuric acid and 0.1 NK₂SO₄. The data are supplemented by intrinsic viscosity measurements used to detect the possible effects of association, by differential refractometry providing a measure of the refractive index increments in mixed solvents (H₂O, H₂SO₄ and K₂SO₄) and by spectrophotometry for the extinction coefficient needed in the correction of attenuation in light scattering studies. The results show 〈D〉Z = 2.11 × 10^?5$\text{M}\text{?}{}_{\mathrm{<mtext>W</mtext>}}{}^{\mathrm{?0.75}}\text{cm}{}^{\mathrm{?2}}\text{s}{}^{\mathrm{?1}}$ in reasonable agreement with an average of many of the published intrinsic viscosity data obeying [η] = 1.09 × 10?3 M_w^1.25 ml g^?1 and _w expressed in g mol^?1.     

Macromolecular properties of heparin in dilute solution: 2. Dimensional parameters as a function of pH,ionic strength and desulphation

A bovine heparin fraction was examined by sedimentation analysis and intrinsic viscosity measurements as a function of ionic strength in the range of 0·1 to 1·0 M, and at pH 2·5 and 6·0. The following experimental parameters were obtained: M, S⁰_20,W, D⁰_20,W, $\text{V}\text{?}$, and [η]. Other physical parameters were calculated based on a random coil model (supported by the theory of Mandelkern and Flory) e.g., $\text{(}\text{r}\text{?}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, $\text{(}\text{s}\text{?}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$. Similar studies were made on a heparin sample as a function of desulphation as resulting from graded mild hydrolysis. Since desulphation is accompanied by decreasing anticoagulant activity of heparin, the latter was correlated with various calculated and measured physical parameters. Significantly $\text{(}\text{r}\text{?}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ decreases with decreased desulphation and therefore decreased biological activity.     

Study of relationship between network structure of g.p.c. gels and molecular size of permeable substance

Attempts were made to correlate the average size of the network of crosslinked vinyl acetate-glycidyl methacrylate (GMA) copolymer to the maximum size of permeable molecules when the copolymers were used as g.p.c. packing materials. The root-mean-square of the end-to-end distance $\text{(}\text{r}\text{?}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ of the hydrodynamic radius $\text{(}\text{s}\text{?}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, which characterizes the maximum extent of the molecules, were calculated. Meanwhile, the average size of the copolymer network, r_c, was estimated from the average molar weight between crosslinkages, this being calculated from the equilibrium rubber elastic modulus, E_r, obtained by dynamic discoelastic measurements. It was found that the maximum size which can permeate the copolymer decreases as the content of GMA in the copolymer increases. From viscoelastic measurements, E_r was found to increase as the content of GMA in the copolymer increases. Further, linear relationships were obtained among r_c, $\text{(}\text{r}\text{?}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, and $\text{(}\text{s}\text{?}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ covering the wide range of the copolymer composition.     

Phosphonitrilic chloride: 21. Synthesis of chelating polymers with cyclophosphazene thiocarbamate and the properties of chelating polymers

Chelating polymers containing copper, nickel and cobalt have been formed from cyclophosphazene thiocarbamate trimer and copper, nickel or cobalt ions. These polymers obtained from the reaction are amorphous and the values of electron conductivity are $\text{2·7 × 10}{}^{11}\text{Ω-}\text{cm}$, $\text{3·6 × 10}{}^{13}\text{Ω-}\text{cm}$ and $\text{1·5 × 10}{}^{13}\text{Ω-}\text{cm}$ for the Cu, Ni and Co polymers respectively. The Cu polymer is the most thermally stable on heating to 500°C in air.     

Excluded chain dimensions and network size in g.p.c.

Attempts have been made to correlate the average network size of polystyrene, poly(methyl methacrylate), poly(methyl acrylate), poly(n-butyl acrylate) and poly(vinyl acetate) gels with the maximum size of the polymer molecule which can permeate the gels. The average size of the network structure (r_c) was estimated from the average molecular weight between crosslinkages (M_c) derived from the glass transition temperatures of the gels. The maximum molecular size which could permeate into the network was expressed as the root-mean-square end-to-end distance [$\text{(}\text{r}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$] of the permeable substance with the molecular weight at exclusion limit (M_lim) obtained by gel permeation chromatography. Both r_c and $\text{(}\text{r}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ decreased with increasing total dose of γ-irradiation or increasing amount of the crosslinking agent. Linear relations were also obtained between r_c and $\text{(}\text{r}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ covering a wide range of total dose and amount of the crosslinking agent.     

Synchrotron radiation ablation of polymers having double bonds in their main chains

Polyacetylene (PA), poly(cis- and trans-1,4-butadiene)s (cis- and trans-PBs), and poly(p-phenylene vinylene) (PPV) were ablated by synchrotron radiation (SR), aiming to deposit thin, uniform films of each on a substrate. When PA was irradiated by SR, gaseous phenyl compounds were produced, and a thin amorphous film was deposited on the substrate, exhibiting no characteristics of PA. In the cases of PPV and trans-PB, the source materials were reproduced in the form of thin film on the substrate by SR ablation. When alkali halides, e.g. NaCl and KBr, were used as deposition substrates, PPV was deposited, in an ordered way, on their cleavage surfaces. However, the deposited film of trans-PB by SR ablation was non-crystalline, because it was produced as a copolymer by 1,4- and 1,2-addition polymerizations of ablated butadiene-based fragments. In comparison, thin films of these polymers were also prepared by thermally evaporating them in a vacuum. When trans-PB and PPV were thermally evaporated, thin films with chemically and structurally identical features to the source polymers were produced, respectively. In contrast, a deposited film from cis-PB by SR ablation consisted of carbon compounds, showing no sign of hydrocarbon compounds in it, while trans-PB was produced from cis-PB by thermal vapor deposition.     

Viscosity of heparin in formamide and glycerol

The viscosity of heparin was examined in pure glycerol, formamide and in mixtures of the two solvents. This study confirms that the equation $\text{η}{}_{\mathrm{sp}}\text{c}\text{= [η]}{}_{\mathrm{\infty }}\text{[1 +}\text{k}\text{(c)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{]}$, where [η]_∞ is the shielded intrinsic viscosity, adequately describes the concentration dependence of the reduced viscosity of the polyelectrolyte, heparin. The [η]_∞ linearly increases with the dielectric constant of the solvent.     

Network of γ-irradiated poly(vinyl alcohol) beads

The crosslinking of poly(vinyl alcohol) beads was performed by γ-ray irradiation. The maximum molecular size, M_lim, which can permeate through beads, was obtained by eluting poly(ethylene glycol) through a column packed with beads. The root-mean-square of the end-to-end distance $\text{(}\text{r}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and that of the hydrodynamic radius $\text{(}\text{s}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ were also calculated. Meanwhile, the average size of the network of the beads, r_c, was estimated from the average molecular weight between crosslinkages, M_c, which was derived from the glass transition temperatures of crosslinked and non-crosslinked poly(vinyl alcohol) beads. r_c values of poly(vinyl alcohol) beads decreased as the total dose of γ-irradiation increased when dry poly(vinyl alcohol) beads were γ-irradiated, while the values were almost constant when poly(vinyl alcohol) beads swollen in water were γ-irradiated. Further, linear relations were obtained among r_c, $\text{(}\text{r}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, and $\text{(}\text{s}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ covering the wide range of total dose.     

The unperturbed molecular dimensions of poly(ethylene oxide) in aqueous solutions from intrinsic viscosity measurements and the evaluation of the theta temperature

Intrinsic viscosity measurements were carried out on five well characterized fractions of poly(ethylene oxide) in aqueous solutions at 24.9°, 34.9°, and 45.5°C. The Stockmayer-Fixman extrapolation was applied to the data: it yields the unperturbed dimensions K₀ of the chain. The unperturbed root-mean-square end-to-end distance $\text{〈}\text{R}\text{?}{}^2\text{〉}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}_0$ calculated for the polymer fractions in water indicate that the polymer molecules are expanded in this solvent as the temperature is raised. The temperature coefficient of unperturbed dimension, $\text{d In}\text{〈}\text{R}\text{?}{}^2\text{〉}{}_0\text{d}\text{t}\text{= 0.024}\text{K}{}^{\mathrm{?1}}$, calculated for poly(ethylene oxide) in water using the present data is about 100 times higher than the literature values of 0.23 (±0.02) × 10^?3 K^?1 and 0.2 (±0.2) × 10^?3 K^?1, respectively, obtained from force-temperature (‘thermoelastic’) measurements on elongated networks of the polymer in the amorphouse state and form viscosity measurements on this polymer in benzene. A value of θ=108.3°C was obtained from the temperature dependence of the interaction parameter B in the Stockmayer-Fixman equation.     

Isomerization of olefins and substituted olefins catalyzed by nickel complexes

The catalytic activity of several Ni (diphosphine)₂/acid homogeneous systems (acid = HCN, CF₃COOH, CCl₃COOH, and H₂SO₄) in the double bond and cistrans isomerizations of olefins has been tested with the following compounds: pentene-1, cis-pentene-2, trans-pentene-2, allyl benzene, allyl cyanide, allyl alcohol. The catalytic efficiency of the Ni(diphosphine)₂/acid systems depends markedly on the nature both of the diphosphine and of the acid employed. When the diphosphine is 1,4-bis(diphenylphosphino)butane and acid = HCN a particularly efficient catalytic system is formed in situ and only in the case of the allyl cyanide is the isomerization limited. During the isomerization of pentene-1, the stereoselectivity in the formation of the cis-2 and trans-2 isomers is quite dependent on the nature of the cocatalyst. It is proposed that a σ-alkyl mechanism is operating in the $\text{Ni(O)}\text{CF}{}_3\text{COOH}$ system and a π-allyl one in the case of $\text{Ni(O)}\text{HCN}$.     

Thermomechanical heat of deformation studies on cis-polybutadiene

Thermomechanical heat of torsional deformation measurements have been made on crosslinked cis-polybutadiene by means of a Calvet microcalorimeter operated at 30°C. When corrected for volume changes utilizing the Gaussian statistical theory of elasticity, the data gave a value for the relative energy contribution to the torsional couple, $\text{M}{}_{\mathrm{e}}\text{M}$, of 0.14 ± 0.02. Measurements were also made on a sample subjected to simple tensile deformations. The relative energy contribution to the tensile force ($\text{f}{}_{\mathrm{e}}\text{f}$) was found to agree within experimental error with the value obtained for $\text{M}{}_{\mathrm{e}}\text{M}$, and the two results gave an average value for din $\text{〈r}{}^2{}_0\text{〉}\text{d}\text{T}$ of 4.1 × 10^?4 K^?1.