Dilute solution properties of polylaurolactam

For a number of fractions and unfractionated samples of polylaurolactam, molecular weights ($\text{M}{}_{\mathrm{<mtext>w</mtext>}}\text{= 1 × 10}{}^4\text{?12·5 × 10}{}^4$) were measured by the light-scattering method in a mixed solvent of m-cresol with 60 vol. % 2,2,3,3-tetrafluoropropanol; intrinsic viscosities were determined in m-cresol and 96% H₂SO₄, and the constants of the Mark-Houwink equation were calculated. The calculated values of the characteristic ratio of unperturbed dimensions (virtually identical for m-cresol and 96% H₂SO₄) were compared with the respective values for polypyrrolidone and polycaprolactam. It was found that the higher frequency of the CONH-groups reduces the rigidity of the polyamide chain.     

Dilute solution properties of poly(N-vinyl-3,6-dibromo carbazole)—III. Phase equilibrium studies

The phase relationships of poly(N-vinyl-3,6-dibromo carbazole) (PVK-3, 6-Br₂) were examined for four solvents, viz, o-chlorophenol, p-chloro-m-cresol, o-dichlorobenzene and bromobenzene. Upper critical solution temperatures (UCST) have been determined for solutions of PVK-3,6-Br, fractions in o-chlorophenol and p-chloro-m-cresol over the molecular weight range $\text{M}{}_{\mathrm{<mtext>w</mtext>}}\text{× 10}{}^{\mathrm{?4}}\text{= 125.0}\text{to}\text{4.8}$. The Flory temperature, θ, obtained from UCST for the PVK-3,6-Br₂/o-chlorophenol and PVK-3,6-Br₂/p-chloro-m-cresol systems are 66.0 and 112.9°C, respectively. The θ-temperatures were checked against molecular weight and viscosity data to determine the Mark-Houwink equations for these two theta solvents, with satisfactory agreement. The relations are

$\text{[ν] = 27.5}{}_4\text{× 10}{}^{\mathrm{?10}}\text{×}\text{M}{}^{0.50}{}_{\mathrm{<mtext>w</mtext>}}\text{(o-}\text{chlorophenol}\text{, 60.0°}\text{C}$

$\text{[ν] = 30.2}{}_4\text{× 10}{}^{\mathrm{?10}}\text{×}\text{M}{}^{0.50}{}_{\mathrm{<mtext>w</mtext>}}\text{(p-}\text{chloro}\text{-m}\text{cresol}\text{, 112.9°}\text{C}$

The characteristic ratio C_∞ = 〈R²〉₀/nl² was found to be 16.6 in o-chlorophenol at 60.0°C and 17.6 in p-chloro-m-cresol at 112.9°C. The value of the characteristic ratio C_∞ of PVK-3,6-Br₂ is of the same order of that for poly(N-vinyl carbazole). This indicates that the bromine atoms at the 3 and 6 (meta) positions have only an inappreciable effect on the hindering potential for rotation about the CC bond. This agreement of C_∞ for both polymers may also be taken as indicating that the effect of interaction between polar groups at the m-position on the hindering potential for rotation is small. The phase diagrams of PVK-3,6-Br₂ obtained in o-dichlorobenzene and bromobenzene seem to be characteristic of organized phase structures such as those found in systems exhibiting thermoreversible gelation. Light scattering measurement on PVK-3,6-Br₂ dissolved in o-dichlorobenzene, a gelation promoting solvent, and tetrahydrofuran, a very good solvent, strongly indicate that the macromolecular species in o-dichlorobenzene contain some extent supermolecular structures (aggregates, association of chain segments, etc.). These characteristic structures of PVK-3,6-Br₂ in o-dichlorobenzene and bromobenzene at 25°C are also characterized by high values of the Huggins' constant k′; for tetrahydrofuran solutions, the k′ values were in the range normally found for many good solvent-polymer systems.     

Etude des volumes specifiques partiels de polystyrenes-modeles—Influence de la masse moleculaire et de la nature des groupements terminaux

It is well known that the apparent specific volume η₂ of a polymer may be expressed by the following relationship: $\text{η}{}_2\text{= η}{}_{\mathrm{m}}\text{+ K/}\text{M}{}_{\mathrm{n}}$ where M?_n is the number-average molecular weight of the polymer, η_m the specific volume of the infinite polymer, and K a constant. We have shown that this relationship is valid for low molecular weight polystyrenes ($\text{M}{}_{\mathrm{n}}\text{< 4·10}{}^4$) with different end-groups, independently of the nature of the solvent. The K values (and variations with the solvent and with the nature of the end-groups) may be predicted through simple calculations proposed here. We conclude that η_m does not represent the specific volume of the infinite polymer, since we observe a rapid decrease of η₂ for increasing M (when $\text{M}{}_{\mathrm{n}}\text{< 4·10}{}^4$). The decrease is much greater than expected from the relationship $\text{η}{}_2\text{= ? (1/}\text{M}\text{)}$.     

Ternary interaction parameters in n-hexane/butanone (MEK)/poly(dimethylsiloxane) (PDMS) and n-heptane/MEK/PDMS systems

Second virial coefficients, A₂, intrinsic viscosities, [η], and solvation preferential coefficients, γ, for the ternary systems n-hexane, HEX, (1)/butanone, MEK, (2)/poly(dimethylsiloxane), PDMS, (3) and n-heptane, HEP, (1)/MEK (2)/PDMS (3) have been determined at 20.0°. Binary interaction parameters, g₂, have also been measured by light scattering. Inversion in γ at $\text{u}{}_2\text{? 0.15}$ in the HEX system and at $\text{u}{}_2\text{? 0.22}$ in the HEP system takes place. The inversion points are accompanied by smooth maxima in A₂ and in [η]. Both systems show a weak cosolvent character. Theoretical γ's derived, according to Flory-Huggins and Flory-Prigogine-Patterson, are compared with experimental values. The evaluation of the ternary interaction potential, g_T, and its dependence on system composition allow evaluation of the binary interaction potentials and their dependence on polymer concentration.     

Excess volumes and isentropic compressibilities for (2-ethoxyethanol + n-heptane) at 298.15 K

Excess volumes and ultrasonic speeds have been measured for (2-ethoxyethanol + n-heptane) at 298.15 K. Isentropic compressibilities, excess isentropic compressibilities, and the partial molar excess quantities $\text{K}{}_{\mathrm{<mtext>S,\; </mtext><mtext>i</mtext>}}{}^{\mathrm{<mtext>E</mtext>}}\text{= ?(}\text{?V}{}_{\mathrm{i}}{}^{\mathrm{E}}\text{?p}\text{)}{}_{\mathrm{S}}$ were calculated from the results. The excess volume is positive over the entire mole-fraction range, whereas the curves for the excess isentropic compressibility is sigmoid with negative values occurring at mole fractions of 2-ethoxyethanol greater than 0.35. A qualitatitive interpretation of the results is presented.     

A study of the chemical and physical structure of polycaproamide obtained in anionic polymerization of caprolactam in solvent

The chemical and physical structure of polycaproamide obtained by low temperature anionic polymerization of caprolactam in solvent in the presence of the sodium salt of caprolactam and carbon dioxide, has been investigated. Solution behaviour of unfractionated and fractionated samples of polymer in 96% sulphuric acid, m-cresol and mixed solvent (2,2,3,3-tetrafluoropropanol-10% H₂O-0.1 M LiCl) was studied by viscosity measurements. The constancy of the Huggins viscometric coefficient K′ in 96% H₂SO₄ and m-cresol enables determination of limiting viscosity number from measurement at one concentration. On the basis of number-average molecular masses and limiting viscosity numbers, the constants of the Mark-Houwink equation were calculated for $\text{M}{}_{\mathrm{<mtext>n</mtext>}}$ in the range 3 × 10³ to 62 × 10³. They are fairly similar to established values for hydrolytic and anionic polycaproamides. The results confirmed our previous suggestion concerning the linear structure of this polyamide. X-ray analysis indicated high degree of crystallinity. The final, chemical treatment causes changes in chemical and physical structure of this polycaproamide. It differs in some respects from hydrolytic and anionic polycaproamides produced in bulk polymerizations of caprolactam. The findings lead to an understanding of several properties of the polycaproamide.     

Dilute and concentrated solutions of polystyrene in trans-decalin close to and far from the θ-temperature—II. Osmotic pressure measurements

Osmotic pressure measurements on polystyrene ($\text{M}{}_{\mathrm{n}}\text{= 396. 000}$) in trans-decalin for concentrations up to 140 kg m^?3 and from 20 to 40 are reported. The θ-temperature is 20.8 . The ratio

where c⁺ is the concentration at which a homogeneous segment distribution is assumed to prevail, increases with temperature up to the plateau value of 0.7. From the temperature dependence of the osmotic pressure, the partial molar enthalpy. Δh₁, and entropy, Δs₁. of mixing are found to be positive. The solvent-solute interaction parameter increases linearly with concentration at all temperatures.     

Ultrasonic speeds and isentropic compressibilities of 2-methylpentan-1-ol with hexane isomers at 298.15 K

Ultrasonic speeds were determined for binary mixtures of 2-methylpentan-1-ol with n-hexane and each of its four isomers. Measurements were made over the whole mole-fraction range with particular attention given to the region of high dilution with respect to the alcohol. The results were combined with excess molar volumes reported previously to obtain values of the excess molar quantity $\text{K}{}_{\mathrm{<mtext>S,</mtext><mtext>m</mtext>}}{}^{\mathrm{<mtext>E</mtext>}}\text{= ?(}\text{?V}{}_{\mathrm{m}}{}^{\mathrm{E}}\text{?p}\text{)}{}_{\mathrm{s}}$ and the corresponding partial molar derivatives.     

Crystallographic shear structures derived from CrO2: An electron microscopic study

We have established by electron microscopy and electron diffraction the existence of several crystallographic shear phases in the family of chromium oxides Cr_nO_2n?1, where n = 4 and 6. As in the systems Ti_nO_2n?1 and V_nO_2n?1, the phases are based on crystallographic shear on the planes {121}. A further series of phases found in this study show a superlattice along $\text{g}\text{?}{}_{210}$ and bear similarities to the M_mO_2m?2 phases found by Gibb and Anderson in the Ga₂O₃TiO₂ system.     

Thermophysical properties of the intermetallic Mn3MN perovskites III. Heat capacity of the solid solution Mn3.2Ga0.8N

The heat capacity of the solid solution Mn_3.2Ga_0.8N was measured between 5 to 330 K by adiabatic calorimetry. A sharp anomaly with first-order character was detected at T_A = (160.5±0.5) K, corresponding to a magnetic rearrangement and a lattice expansion. No sharp anomaly was observed at T_c ≈ 260 K where the magnetic ordering takes place; instead, a smooth shoulder was detected. The thermodynamic functions at 298.15 K are $\text{C}{}_{\mathrm{<mtext>p,</mtext><mtext>m</mtext>}}\text{R}\text{= 15.16}$, $\text{S}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{R}\text{= 18.57}$, $\text{{H}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(T)?H}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(0)}}\text{R}\text{= 2896}\text{K}$, $\text{?{G}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(T)?H}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(0)}}\text{RT}\text{= 8.85}$. At low temperatures the coefficient for the linear electronic contribution to the heat capacity was derived: γ = (0.031±0.003) J·K^?2·mol^?1. Moreover, the different contributions to the heat capacity were obtained and the electronic origin of the phase transitions was established.     

Preparation and properties of PdPSe single crystals

Single crystals of PdPSe were shown to be n-type semiconductors. Weak Pauli paramagnetic behavior was observed, which is consistent with the presence of delocalized electrons. Electrical measurements showed a room-temperature resistivity ? = 70 ohm-cm, activation energy of resistivity E_a = 0.32 eV, and Hall mobility μ = 34 cm² V^?1 sec^?1. Photoelectronic measurements in aqueous solutions of $\text{I}{}^{\mathrm{?}}\text{I}{}^{\mathrm{?}}{}_3$ indicate that PdPSe has high quantum efficiencies below 800 nm. The indirect optical band gap is 1.28(2) eV.     

Hydrodynamic properties and statistical coil dimensions of poly(o-chlorostyrene)

The theta temperature for the system poly(o-chlorostyrene)-methyl ethyl ketone has been determined as 24·5°. The samples used in the determination were prepared by radical polymerization. The dependence of intrinsic viscosity on molecular weight has been measured in methyl ethyl ketone at 24·5° and found to be $\text{η}{}_{\mathrm{\theta }}\text{= 4·68 × 10}{}^{\mathrm{?4}}\text{M}{}_{\mathrm{<mtext>w</mtext>}}{}^{\mathrm{<mtext>M1</mtext><mtext>2</mtext>}}$. The ratio 〈s₌²〉/M was found, by light scattering, to be 5·60 × 10^?18 cm². Analysis of the solution properties indicates that the Kurata-Yamakawa theory is valid in the vicinity of the Flory temperature (UCST).     

KxP2W2O16: A bronze with a tunnel structure built up from PO4 tetrahedra and WO6 octahedra

The structure of a $\text{K}{}_{\mathrm{x}}\text{P}{}_2\text{W}{}_4\text{O}{}_{16}\text{(x ? 0.4)}$ crystal was established by X-ray analysis. The solution in the cell of symmetry $\text{P2}{}_1\text{m}$, with a = 6.6702(5), b = 5.3228(8), c = 8.9091(8) Å, β = 100.546(7)°, Z = 1, has led to R = 0.033 and R_w = 0.036 for 2155 reflections with $\text{σ(I)}\text{I}\text{≤ 0.333}$. This structure can be described as two octahedra-wide ReO₃-type slabs connected through “planes” of PO₄ tetrahedra. A new structural family K_xP₂W_2nO_6n+4 can be foreseen which is closely related to the orthorhombic P₄W₈O₃₂ and the monoclinic Rb_xP₈W_8nO_24n+16 series.     

Absolute bestimmung der molekulargewichtsverteilung von anionisch und radikalisch polymerisierten polystyrolen durch lichtstreuung

The scattering function P₀ for classical elastic light scattering is specified for several molecular weight distribution functions (Schulz-, Square root-, Maxwell-, Normal-, Poisson-, Logarithmic-normal-distribution function). Precision measurements on anionic polymerized polystyrene from Pressure Chemical Co. $\text{(}\text{M}{}_{\mathrm{w}}\text{= 2 · 10}{}^6\text{and}\text{M}{}_{\mathrm{w}}\text{= 6,7 · 10}{}^6\text{)}$ and radical initiated polystyrene were performed in transdecalin with the light scattering photometer Fica 50. Comparison of experimental results with theoretical curves indicate that the anionic polystyrenes exhibit a broader distribution than given by Pressure Chemical Co. The distribution of the radical polystyrene conforms with distributions found by other methods.     

Polymérisation cationique du chloro-1 butadiène et copolymérisation avec l'isobutène

The cationic homopolymerization of 1-chlorobutadiene and its copolymerization with isobutene have been carried out in dichloromethane solution. The catalyst-cocatalyst pairs used were AlEt₂Cl-(CH₃)₃CCl and AlEtCl₂-(CH₃)₃CCl. In the latter case, the use of (CH₃)₃CCl was not necessary. According to experimental conditions, high molecular weight copolymers ($\text{M}{}_{\mathrm{n}}\text{= 200,000}$) insoluble in CH₂Cl₂, or soluble low polymers ($\text{M}{}_{\mathrm{n}}\text{= 20,000}$) were obtained. Homopoly-1-chlorobutadienes were soluble low molecular weight polymers ($\text{M}{}_{\mathrm{n}}\text{= 10,000}$). The 1-chlorobutadiene units in the polymers are nearly exclusively 3,4 (mainly trans). Consequently, this method is not convenient to prepare elastomers with a 1,4 structure similar to that of chlorinated butyl rubber.     

Dilute solutions of nylon 12—II. Relationship between intrinsic viscosity and molecular weight

Samples of poly(12-dodecanelactam) (polylaurolactam, nylon 12) with $\text{M}$_n 1 × 10³?33 × 10³ were prepared. Polymerizations initiated with water or with lauric acid proceeded under conditions for minimum changes in end-group concentration. Values of $\text{M}$_n were calculated from the end-group content and $\text{M}$_n from light scattering in the mixture m-cresol/60 vol% of 2.2,3,3-tetrafluoropropanol. From measurements of intrinsic viscosity in m-cresol, the relationship [n] ? $\text{M}$_n was established in the given range of $\text{M}$_n. The relationship [n] ? $\text{M}$_w for $\text{M}$_w from 3.3 × 10³ to 125 × 10³ has been established.     

The thermal polymerization of styrene at temperatures up to 250°

The kinetics of the thermal polymerization of styrene have been studied over the range 60–250°. The overall energy of activation was 86 ± 2 kJ/mole, a value identical to that obtained for the thermal polymerization of styrene in diethyl adipate. As expected, the molecular weight of the polymer decreases with increase in the temperature of the polymerization, and the ratio $\text{M}{}_{\mathrm{<mtext>w</mtext>}}\text{M}{}_{\mathrm{<mtext>n</mtext>}}$ becomes greater than 2 for polymer formed at above 140°. The plot of log ($\text{1}\text{M}{}_{\mathrm{<mtext>n</mtext>}}$) against (absolute temperature)^?1 can be represented by two straight lines yielding 24.5 and 32,0 kJ/mole for the activation energies at temperatures below 120° and above 140°, respectively. The former value is in keeping with the molecular weight being controlled by chain transfer with monomer; the latter value would be that expected if the termination process controls the molecular weight of the polymer. Mark Houwink relationships between intrinsic viscosity and $\text{M}$_n and $\text{M}$_w have been found to apply to polymer samples when the molecular weight averages were determined by osmometry and by light scattering. However, deviations were found for low molecular weight material when measured using gel permeation chromatography. The K values were considerably lower, and the α values higher than reported in the literature.     

Estimation of the characteristic ratio of poly[2-(triphenylmethoxy)ethyl methacrylate] from hydrodynamic properties of its dilute solutions

Properties of poly[2-(triphenylmethoxy)ethyl methacrylate] (PTEMA) molecules in solutions (under O-conditions and in “good” solvents) were investigated by the light scattering, sedimentation, viscometric and by phase equilibria methods. The O-temperature (47°) was determined for the system mesitylene-PTEMA. Unusual correlations of hydrodynamic data with molecular weight are discussed and slight branching of polymer chains is accepted as a probable explanation. Data for mesitylene solutions under O-conditions are used to estimate the characteristic ratio of PTEMA molecules ($\text{R}{}_0{}^2\text{/nl}{}^2\text{= 19}$).     

A viscometric study of poly(methyl methacrylate) in 2-alkoxyethanols

θ-Conditions, the temperature coefficient of unperturbed dimensions of the macromolecules and the thermodynamic interaction parameters ψ and κ were determined for solutions of poly(methyl methacrylate) in 2-alkoxyethanols (methoxy, ethoxy and butoxy). The results for this series of solvents fit the data reported for other solvents and dln $\text{r}{}_0{}^2\text{/}\text{d}\text{T = 2.6 × 10}{}^{\mathrm{?3}}\text{K}{}^{\mathrm{?1}}$. The dependence of parameters ψ and κ exhibited deviations from the theoretical dependence, mainly near the limiting value ψ = 0.5.     

A theory of viscosity of dilute and moderately concentrated polymer solutions

A model theory of viscosity η for moderately concentrated polymer solutions is based on the assumption of a “local viscosity” effect and intermolecular hydrodynamic and thermodynamic interactions. It is shown that η is given by

$\text{η = η}{}_{\mathrm{o}}\text{{1 + γc[η]}}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{·}\text{exp}\text{H}{}_{\mathrm{o}}\text{RT}\text{aø}\text{1 ? aø}$

where γ is 0–0.4 and depends on the quality of the solvent, a varies between 0,4 and 0.8 and depends on the fraction of the “free volume” of the systems, H₀ is the activation energy of the solvent and π is the polymer volume concentration. The dependence of η and “activation energy” of π and T for various molecular weights and qualities of solvents is described quantitatively. Anomalous dependences of [η] and of η on M for low polymer are obtained. An expression for η is proposed:

$\text{η}\text{η}{}_{\mathrm{o}}{}^{\mathrm{<mtext>1\; ?\; 2</mtext><mtext>K</mtext>}}\text{= {1 + (1 ? 2K)c[η]}F(π)}$

where K is the Huggins-Martin coefficient and F(π) = 1 for most solutions when T is > T_g. For poor solvents the H vs c curve (where H is the activation energy of η of solution) has a minimum value at moderate concentrations. For good solvents, H depends slightly on the molecular weight according to an empirical equation:

$\text{H = H}{}_{\mathrm{o}}\text{+}\text{660}\text{α}{}^3\text{1}\text{n}\text{η}\text{η}{}_{\mathrm{o}}$

Expressions are given from the viscosities of solutions of miscible and also solutions of immiscible polymers.