Properties of extremely high molecular weight polystyrene in solution

Extremely high molecular weight polystyrenes with a $\text{M}\text{?}{}_{\mathrm{w}}$ in the range 10.8 × 10⁶ to 2.2 × 10⁷ were prepared by emulsion polymerization initiated with a heterogeneous initiator at 30°C, which has a ‘living character’. Samples of polystyrene were characterized by light scattering and viscometry in toluene and benzene at 25°C, and in θ-solvent cyclohexane at 34.8°C. Also determined were the relationships of mean-square radius of gyration 〈s²〉 (m²) and the second virial coefficient A₂ (m³ mol kg^?2) on the molecular weight, which for toluene and benzene are described in equations: Toluene (25°C) $\text{〈s}{}^2\text{〉=1.59 × 10}{}^{\mathrm{?23}}\text{M}\text{?}{}_{\mathrm{w}}{}^{1.23}$; $\text{A}{}_2\text{=4.79 × 10}{}^{\mathrm{?3}}\text{M}\text{?}{}_{\mathrm{w}}{}^{\mathrm{?0.63}}$; Benzene (25°C) $\text{〈s}{}^2\text{〉=1.23 × 10}{}^{\mathrm{?22}}\text{M}\text{?}{}_{\mathrm{w}}{}^{1.20}$; $\text{A}{}_2\text{=2.59 × 10}{}^{\mathrm{?3}}\text{M}\text{?}{}_{\mathrm{w}}{}^{\mathrm{?0.59}}$. The parameters in the Mark-Houwink-Sakurada equation were established, for extremely high molecular weight polystyrene in toluene and in benzene, at 25°C into the form giving for $\text{[η] (}\text{m}{}^3\text{kg}{}^{\mathrm{?1}}\text{): [η] = 8.52 × 10}{}^{\mathrm{?5}}\text{M}\text{?}{}_{\mathrm{w}}{}^{0.61}$; $\text{[η] = 1.47 × 10}{}^{\mathrm{?4}}\text{M}\text{?}{}_{\mathrm{w}}{}^{0.56}$. The mentioned relations, as well as the obtained values of Flory parameter ?₀ and of ratio $\text{[η]}\text{M}\text{?}{}_{\mathrm{w}}{}^{0.5}$ were compared with solution properties of high molecular weight polystyrene with narrow molecular weight distribution prepared by anionic polymerization by Fukuda et al.     

Pressure dependence of upper critical solution temperatures in the polystyrene - cyclohexane system

The pressure dependence of the upper critical solution temperature $\text{(}\text{d}\text{T}\text{d}\text{p}\text{)}{}_{\mathrm{c}}$ in the polystyrene-cyclohexane system has been measured over the pressure range of 1 to 50 atm. The value of $\text{(}\text{d}\text{T}\text{d}\text{p}\text{)}{}_{\mathrm{c}}$ determined over the molecular weight (M_w) range of 3.7 × 10⁴ to ～145 × 10⁴ greatly depends on the molecular weight of polystyrene. The value of $\text{(}\text{d}\text{T}\text{d}\text{p}\text{)}{}_{\mathrm{c}}$ for a polystyrene solution of low molecular weight (M_w = 3.7 × 10⁴) is positive (3.14 × 10^?3 degree atm^?1), while the values are negative (?0.52 × 10^?3～?5.64 × 10^?3 degree atm^?) for solutions of polystyrene over the high molecular weight range of 11 × 10⁴ to ～145 × 10⁴. The Patterson-Delmas theory of the corresponding state and the newer Flory theory have been used to explain this behaviour.     

Small-angle neutron scattering studies of isotropic polypropylene

Small-angle neutron scattering studies have been made of molten and crystalline polypropylene using samples containing small amounts of deuterated polypropylene in a protonated polypropylene matrix. The specimens were characterized by small- and wide-angle X-ray scattering to determine the d-spacing and the degree of crystallinity χ and by gel permeation chromatography to determine molecular weight, M_w, and molecular weight distribution. The degree of crystallinity was varied from 0.5 to 0.7, the d-spacing from 120 to 250 Å and the molecular weight from 34 000 to 1 540 000. Clustering was not observed. The radius of gyration $\text{〈s}{}^2\text{〉}{}_{\mathrm{w}}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ of the tagged molecules was approximately proportional to $\text{M}{}_{\mathrm{w}}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and almost independent of d and χ. In the melt similar values were obtained which are, within experimental uncertainties, the same as in a θ-solution. For 〈s²〉_wk²? 1 the scattering law approaches a k^?2 dependence. The results are discussed with reference to the chain-folded model but a fit cannot be obtained over all molecular weights. A simple random coil model fits the neutron scattering data partly but this does not explain the origin of the d-spacing.     

Self-diffusion of poly(ethylene oxide) in aqueous dextran solutions measured using FT-pulsed field gradient n.m.r.

Transport in ternary polymer₁, polymer₂, solvent systems has been investigated using an n.m.r. spin-echo technique. The dependence of the self-diffusion coefficient of poly(ethylene oxide) polymers on the concentration and molecular size of dextran in aqueous solution has been measured. Monodisperse poly(ethylene oxide) fractions ($\text{M}\text{?}{}_{\mathrm{w}}\text{=7.3×10}{}^4$, 2.8·10⁵ and 1.2·10⁶) and dextrans ($\text{M}\text{?}{}_{\mathrm{w}}\text{=2·10}{}^4$, 1·10⁵ and 5·10⁵) have been employed over a range of concentration up to the miscibility limit in each system. It is found that when the molecular size of the diffusant is commensurate with or exceeds that of the matrix polymer, a relationship of the form: $\text{(}\text{D}\text{D}{}_0\text{)}{}_{\mathrm{<mtext>PEO</mtext>}}\text{=}\text{exp}\text{?k(C[η])}$ is applicable, where C[η] refers to the dextran component and is considered to describe the extent of coil overlap in concentrated solution. ($\text{D}\text{D}{}_0$) is independent of the molecular size of the poly(ethylene oxide), at least in the range studied (M_w<300 000).     

Unperturbed dimensions of poly(phenyl acrylate)

Thirteen fractions of poly(phenyl acrylate) have been prepared with weight-average molecular weight ranging from 0.158 × 10⁶ to 2.57 × 10⁶ g mol^?1. The temperature coefficient of the unperturbed dimensions and the glass transition temperature were found to be ?1.8 × 10^?3 deg^?1 and 55.6°C respectively. Good accord was obtained among different methods for establishing θ-conditions of 11.5°C in ethyl lactate. From viscometry, osmometry and light scattering under θ-conditions, as well as in a good solvent, the unperturbed dimensions were determined via several procedures yielding a value of $\text{[〈r}{}^2\text{〉}{}_{\mathrm{0w}}\text{M}\text{?}{}_{\mathrm{w}}\text{]}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 6.0 (±0.2) × 10}{}^{\mathrm{?9}}\text{cm g}{}^{\mathrm{<mtext>?1</mtext><mtext>2</mtext>}}\text{mol}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$. This corresponds to a steric factor υ = 2.37 (±0.08) and a characteristic ratio C_∞ = 11.3 (±0.8). The polymer chain is thus more rigid than poly(methyl acrylate), but less rigid than poly(phenyl methacrylate). With respect to its T_g and flexibility, poly(phenyl acrylate) bears a strong similarity to poly(benzyl methacrylate).     

Poly(sulphopropylbetaines): 2. Dilute solution properties

Solution properties of a series of aromatic ($\text{5 × 10}{}^3\text{<}\text{M}\text{?}{}_{\mathrm{w}}\text{< 2.5 × 10}{}^5$) and aliphatic ($\text{10}{}^6\text{<}\text{M}\text{?}{}_{\mathrm{w}}\text{< 1.2 × 10}{}^7$) poly(sulphopropylbetaines) have been investigated by examining three complementary phenomena: (a) solubility in organic protic solvents; (b) water solubility promoted by various (cloud point titrations), with special emphasis on the influence of the anion polarizability and a comparison between Na⁺ and Ca⁺⁺; (c) hydrodynamic and morphological properties in aqueous NaCl solutions at 25°C, as derived from the Mark-Houwink-Sakurada relations. Chain expansion is a slightly increasing function of the NaCl concentration (≤1 M) but it remains, however, relatively low, even for high molecular weights (α_η < 1.15). With respect to the polymeric amino precursors, the zwitterionic group

enhances chain rigidity (steric factor σ), as a result of its steric hindrance and specific dipolar interactions between neighbouring units.     

Quasi-elastic light scattering from branched polymers: 1. Polyvinylacetate and polyvinylacetate—microgels prepared by emulsion polymerization

Emulsion polymerization of vinylacetate leads to branched polymers which at high monomer conversions form microgels of the shape and size of the latex particles. Quasielastic light scattering measurements from samples in the pre-gel state give at small q² a linear angular dependence of $\text{D}{}_{\mathrm{app}}\text{=}\text{Г}\text{q}{}^2$ which resembles that of randomly branched chain molecules, where Г is the decay constant of the time correlation function. Extrapolation of D_app towards zero scattering angle yields the translational diffusion constant D_z. The diffusion constant follows the molecular weight dependence D_z = 9.78 10^?5M_w^?0.478. The diffusion constant of the microgels, i.e. at molecular weights M_w > 14 10⁶, remains constant because of the finite and constant size of the latex particles. The coefficients k_f and k_D in the concentration dependence of the frictional and diffusion coefficients are related according to the equation $\text{k}{}_{\mathrm{D}}\text{= k}{}_{\mathrm{f}}\text{? 2A}{}_2\text{M}{}_{\mathrm{w}}\text{?}\text{v}\text{?}$ where A₂ is the second virial coefficient and v? the partial specific volume of the particle. The coefficient k_f is calculated from the experimentally determined quantities k_D, A₂ and M_w, and the result is compared with the theory by Pyun and Fixman. Accordingly the branched coils in the pre-gel state resemble soft spheres, but the microgels behave more like spheres of some rigidity.     

Poly(ethyl acrylate) in dilute solution

Poly(ethyl acrylate) (PEA), solution polymerized in methyl ethyl ketone by free radical initiation, was fractionated and the fractions were characterized by light scattering, viscometry and osmometry. Fractions obtained were in the molecular weight range of 0·3 × 10⁶ to 1·6 × 10⁶ with a polydispersity of 1.40. The following Mark-Houwink relations were established:

$\text{[η]}{}^{\mathrm{<mtext>35°</mtext><mtext>C</mtext>}}{}_{\mathrm{<mtext>acetone</mtext>}}\text{=4·15×10}{}^{\mathrm{?2}}\text{M}{}^{\mathrm{0?61}}{}_{\mathrm{W}}$

$\text{[η]}{}^{\mathrm{<mtext>35°</mtext><mtext>C</mtext>}}{}_{\mathrm{<mtext>MEK</mtext>}}\text{=2·03×10}{}^{\mathrm{?2}}\text{M}{}^{\mathrm{0?66}}{}_{\mathrm{W}}$

$\text{[η]}{}^{\mathrm{<mtext>39.5°</mtext><mtext>C</mtext>}}{}_{\mathrm{<mtext>n-propanal</mtext>}}\text{=7·89×10}{}^{\mathrm{?2}}\text{M}{}^{\mathrm{0?50}}{}_{\mathrm{W}}$

It was found that n-propanol at 39.5°C was a theta solvent for poly(ethyl acrylate) and that acetone was a poor solvent compared to methyl ethyl ketone. A relation between the molecular dimension and the molecular weight was established. It was observed that the chain dimensions of poly(ethyl acrylate) and poly(butyl acrylate) were considerably larger than poly(ethyl methacrylate) and poly(butyl methacrylate) respectively. The validity of various extrapolation procedures that have been proposed for calculating the unperturbed dimensions have been examined. The steric factor for PEA was 2·16 compared to 2·10 for poly(ethyl methacrylate). Root mean square end-to-end distances were calculated from the Debye-Bueche and Kirkwood-Riseman methods and compared with the experimental values.     

Influence of the molecular weight of poly(methyl methacrylate) on fracture surface energy in notched tension

Specimens of poly(methyl methacrylate) (PMMA) were prepared by the radiolysis of a polymer from an initial viscosity average molecular weight of $\text{M}\text{?}{}_{\mathrm{v}}\text{= 1.1 × 10}{}^6$ down to 1.5 × 10⁴. Corresponding values of fracture surface energy, ranging from 3.5 × 10⁵ erg/cm² to 4.5 × 10² erg/cm², were calculated from tensile data using Griffith's equation. A theoretical dependence of fracture energy on molecular weight was derived on the assumption that only molecules exceeding a critical molecular weight can contribute to the work of plastic deformation. Comparison with experimental data indicates this molecular weight to be about 1 × 10⁵. Limitations of the theoretical treatment are discussed.     

Conformation of poly(ethylene oxide) in the solid state,melt and solution measured by Raman scattering

The Raman spectrum of poly(ethylene oxide) (PEO) $\text{M}\text{?}{}_{\mathrm{w}}\text{= 3 × 10}{}^6$ and 6 × 10³ has been measured in bulk as a function of temperature and in aqueous and chloroform solution as a function of solvent concentration. The spectral features are assigned to particular isomeric configurations and the changes on melting are found to be consistent with a helix-coil transition. In both solvents the ordered nature of the polymer is largely lost at a critical concentration, approximately 50% by weight; residual ordering in dilute aqueous solution is lost and the random coil configuration attained only above the melting temperature. The wavenumber change of the 862 cm^?1 mode as a function of water concentration showed formation of a complex involving three water molecules and was consistent with a simple H-bonding model. The differences between the spectra in the two solvents are explained by this H-bonding. The results are in general agreement with n.m.r. work.     

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.     

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.     

Synthesis of electroreactive polymers from poly (m,p-chloromethylstyrene) and copoly (m,p-chloromethylstyrene-styrene)

Polymerization, and copolymerization with styrene, of m,p-chloromethylstyrene have been carried out at 75°C, in chlorobenzene and in the presence of AIBN ($\text{[}\text{AIBN}\text{] ? 6 × 10}{}^{\mathrm{?2}}$, and $\text{12 × 10}{}^{\mathrm{?2}}\text{m}$, respectively). The polymer molecular weights, determined by g.p.c., are: $\text{M}\text{?}{}_{\mathrm{w}}\text{= 8670}$, $\text{M}\text{?}{}_{\mathrm{n}}\text{= 5860}$, and $\text{M}\text{?}{}_{\mathrm{w}}\text{/-M}{}_{\mathrm{n}}\text{= 1.48}$ for the homopolymer, poly(m,p-chloromethylstyrene), (1a); and $\text{M}\text{?}{}_{\mathrm{w}}\text{= 8805}$, $\text{M}\text{?}{}_{\mathrm{n}}\text{= 5144}$, and $\text{M}\text{?}{}_{\mathrm{w}}\text{/-M}{}_{\mathrm{n}}\text{= 1.71}$ for the copolymer, copoly(m,p-chloromethylstyrene-styrene), (2a). A series of phosphine derivatives of both 1a and 2a are prepared by the reaction of the polymers with either chlorodiphenylphosphine/lithium, or diphenylphosphine/potassium tert. butoxide. A number of other potentially electroreactive derivatives of 2a are obtained by reacting the polymer with 2-aminoanthraquinone, 3-N-methylamino-propionitrile, or 2-(2-aminoethyl) pyridine. The phosphinated polymers are reacted with bis-benzonitrilepalladium-(II) chloride to obtain a series of polymer-palladium(II) complexes containing 8.5–12.9% palladium. Similarly, reaction of the last-named bidentate polymeric ligand with cupric acetylacetonate, or cupric sulphate pentahydrate, produces polymer-copper(II) complexes having 5.8, or 3.3% copper, respectively. The inter/intra-chain nature of some of the side reactions during the derivatization of the chloromethylated polymers, and that of the complex formation between transition metal centres and macromolecular ligands, are briefly discussed in view of the experimental results.     

Small-angle neutron scattering studies of molten and crystalline polyethylene

Small-angle neutron scattering studies have been made of molten and crystalline polyethylene using samples containing small amounts of deuterated polyethylene (PED) in a protonated polyethylene (PEH) matrix. Careful studies were made of PED aggregation effects, and by a combination of solution blending techniques and rapid quenching from the melt, it was possible to prepare samples with a statistical distribution of PED molecules in the PEH matrix. Measurements of radius of gyration $\text{(S}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}_{\mathrm{w}}$ at low κ [$\text{κ = (}\text{4π}\text{λ}$) sin $\text{? ≤ 2 × 10}{}^{\mathrm{?2}}\text{A}\text{?}{}^{\mathrm{?1}}$] in the melt and in the solid state gave very similar values which may be summarized as $\text{〈S}{}^2\text{〉}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}_{\mathrm{w}}\text{= (0.46 ± 0.05)M}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}_{\mathrm{w}}$ for both phases. This correspondence of values indicates that on a rapid quench, diffusion is sufficiently slow that the molecule crystallizes with a similar spatial distribution of mass elements to that possessed in the melt. Measurements of scattering data over a wide κ range ($\text{6 × 10}{}^{\mathrm{?3}}\text{≤ κ ≤ 0.12}\text{A}\text{?}{}^{\mathrm{?1}}$) have also been made from samples showing no aggregation effects. Calculations indicate that it is difficult to fit this data in terms of models which postulate adjacent chain re-entry in one crystallographic plane for this type of sample.     

Elution and molecular weight parameters in exclusion chromatography

The mode of the chromatogram is inadequate for characterizing experimental elution curves, which are generally dissymmetrical. It is also dependent on axial diffusion. When the molecular weight distribution is defined either by the generalized exponential function or by the log-normal function, simulation of elution at finite resolution shows that the calibration curve at infinite resolution, independent of the flow rate of the carrier fluid, is approximated validly by correlating the first moment of the chromatogram (MEV) with the geometrical compound average $\text{(}\text{M}\text{?}{}_{\mathrm{n}}\text{M}\text{?}{}_{\mathrm{w}}\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= M}{}_0$. The concentration effect seems to be controlled by a double extrapolation procedure defined by (1) treatment of the chromatograms using the calibration curve at zero concentration ($\text{In}\text{M}{}_0\text{versus}\text{lim}\text{c→o}\text{MEV}$), and (2) linear extrapolation to infinite dilution of the calculated molecular weight averages.     

Effects of dextran molecular weight on graft copolymerization of dextran-methyl methacrylate

Effects of the molecular weight of dextran on its graft copolymerization with methyl methacrylate (MMA), initiated by ceric ammonium nitrate (CAN), have been investigated. The results indicate that grafting (%), graft polymerization (%) (ψ), the overall rate constant (k′) for consumption of Ce⁴⁺, and branch PMMA were influenced significantly by the molecular weight of the backbone polymer dextran. The number of branch PMMA chains per dextran molecule was 0.05 ～ 0.30 for $\text{M}\text{?}{}_{\mathrm{w}}$ 9000 dextran (D1), 0.35 ～ 0.55 for $\text{M}\text{?}{}_{\mathrm{w}}$ 61 000 (D2), and 0.8 ～ 1.6 for $\text{M}\text{?}{}_{\mathrm{w}}$ 196 000 (D3), respectively. The relationship between the rate of graft polymerization and $\text{M}\text{?}{}_{\mathrm{w}}$ (the weight-average molecular weight of dextran) was expressed by the equation: $\text{R}{}_{\mathrm{p}}\text{g = ?A}\text{log}\text{M}\text{?}{}_{\mathrm{w}}\text{+ B}$. Another linear relationship was obtained between In (100 ? ψ) and reaction time (t) for both D1 and D2 samples or In t for D3. Detailed kinetic analysis has been made on the basis of the latter relationship. Mechanical properties were also studied on the moulded sample plates of these copolymers.     

Graft copolymers from azodicarboxylate-functional pre-polymers: 1. Synthesis of azodicarboxylate-functional polystyrene

A synthetic sequence is described for the preparation of polystyrenes in the molecular weight range ($\text{M}\text{?}{}_{\mathrm{<mtext>n</mtext>}}$) 3 × 10³ to 2 × 10⁴ having terminal azodicarboxylate functionality with one functional group per polymer chain. The polymer end groups are characterized spectroscopically at each step in the synthetic sequence. The concentration of azodicarboxylate groups on the polymers is determined spectro-scopically and compared with the $\text{M}\text{?}{}_{\mathrm{<mtext>n</mtext>}}$ of the polymers as calculated from initiator/monomer ratio or as measured by g.p.c. analysis.     

Sedimentation velocity measurements close to the upper critical solution temperature and at θ-conditions: polystyrene in cyclopentane over a large concentration interval

Sedimentation velocity measurements on polystyrene (M = 110 000) in cyclopentane over an extended concentration region and from 5°C (close to the upper critical solution temperature) to 40°C are reported. The concentration dependence parameter (k_s)_w increases from 2 to 5°C to 27 at 40°C. For all temperatures except 5°C, $\text{s}{}_0\text{s}$ vs. w[η]_w shows an upward curvature at w[η]_w ≈ 1; at 5°C, on the other hand, $\text{s}{}_0\text{s}$ is independent of concentration over the region considered. Furthermore, measurements have also been performed at 20°C (θ-conditions) over a large concentration interval for the molecular weights M = 20 400, 390 000 and 950 000. The parameters s₀ and (k_s)_w were both found to be proportional to $\text{M}\text{?}{}^{\mathrm{1/2}}{}_{\mathrm{w}}$. In the ‘hydrodynamically normalized’ plot $\text{s}{}_0\text{s}$ vs. w[η]_w the sedimentation behaviour can approximately be represented by a single curve for all the molecular weights.