Viscosities of dilute solutions of poly (methyl methacrylate) and poly (ethyl methacrylate) in organic solvents

Poly(methyl methacrylate) and poly(ethyl methacrylate) prepared by a benzoylperoxide catalysed polymerization process were fractionated. The variation of the intrinsic viscosity and HUGGINS ' constant with temperature, molecular weight and solvent was studied. From the viscosity data the thermodynamic interaction parameters χ, ψ, k etc., and the solubility parameter of the polymers were evaluated and discussed.     

Viscosities of dilute solutions of poly(tetrahydrofurfuryl methacrylate)

The intrinsic viscosities of seven fractions (from M?_n = 1,69.10⁵ to M?_n = 6,13.10⁵) of poly(tetrahydrofurfuryl methacrylate) in eleven solvents at temperatures between 30° and 50° show the following order: tetrachloroethane > dichloroethane > tetrahydrofuran > chloroform > benzene > bromobenzene > ethyl acetate > carbon tetrachloride > methyl pentyl ketone > acetone > 2-hydroxymethyltetrahydrofuran. Values of HUGGINS slope constants range between 0,34 to 0,48 for the unfractionated polymer and the magnitudes of a and k in the expression [η] = kM^a show little variations with temperature in case of good solvents whereas the opposite is observed in case of poor solvents. The theta temperature for 2-hydroxymethyltetrahydrofuran containing 20% methanol is 31,2 ± 0,3° and 3,49, 5,72, and 4,97 are the values for K₀.10⁴, (r /M)^1/2.10⁹ and (r /Z)^1/2.10⁸, respectively.     

Solution properties of poly(octadecyl methacrylate) in butyl acetate, 1. Dilute Solution

Dilute solutions of poly(octadecyl methacrylate) (PODMA) obtained by radical-initiated polymerization were inverstigated in the theta-solvent butyl acetate (BuAc) by static (SLS) and dynamic light scattering (DLS) and viscometry at six different temperatures between 11°C (near the theta-temperature Θ) and 30°C. The mass-average molar masses ranged from M?_w = 6,2 · 10⁵ g · mol^?1 to 3,2 · 10⁶ g · mol^?1. It was found that PODMA in BuAc behaves in general as expected for linear flexible Gaussian coils in a theta-solvent. The Kuhn length was determined to be 35 Å. At temperatures slightly above Θ = 10,5°C the exponents of the intrinsic viscosity, radius of gyration and hydrodynamic radius versus molar mass relationships lie significantly below 0,5, the expected value for flexible linear chains at theta-conditions. Qualitatively, these findings are explained by a coil contraction due to the different chemical nature of the main chain and the side chains and therefore different polymer-solvent interactions of different parts of the molecules.     

Solution properties of poly(octadecyl methacrylate) in butyl acetate, 2. Semidilute solution

Semidilute solutions of a fraction of poly(octadecyl methacrylate) (PODMA) obtained by radical-initiated polymerization were investigated in the theta-solvent butyl acetate (BuAc) with static and dynamic light scattering (SLS, DLS, resp.) at four different temperatures between 13°C (near theta-temperature Θ) and 70°C. The molar mass of the investigated sample (PODMA 4) was 3,2 · 10⁶ g · mol^?1. A concentration region from dilute to 8 c^* was covered, where c^* = 1/[η] was taken as the coil overlap concentration, [η] denoting intrinsic viscosity. Above c = 3c^* the DLS correlation function exhibited bimodal behaviour at all temperatures. At these concentrations one finds two “apparent” molar masses, radii of gyration and diffusion coefficients for each concentration. The smaller apparent molar masses, smaller radii of gyration and larger diffusion coefficients correspond to characteristics of the transient network. The larger apparent molar masses, larger radii of gyration and smaller diffusion coefficients may be attributed to the formation of inhomogeneities in the semidilute solution.     

On the dilute solution properties of styrene/methyl methacrylate copolymers

The solution properties of unfractionated styrene/methyl methacrylate copolymers were investigated over the entire range of copolymer composition. The Mark-Houwink-Sakurada constants K_η, and a_η of the copolymers, as well as the constants K_Θ and B′ from the Stockmayer-Fixman procedure, related to the unperturbed chain dimensions and to the excluded volume, respectively, seem simply related to those of the parent homopolymers through some composition variables. In most cases, however, equations must be employed which have to be fitted to the experimental data, in order to evaluate parameters which are not otherwise predictable.     

The behaviour of poly(2,3-epoxypropyl methacrylate) in dilute solution

Homopolymers of 2,3-epoxypropyl methacrylate with various molecular masses were prepared by solution polymerization with 2,2′-azoisobutyronitrile as initiator. The effect of polymerization conditions on the molecular parameters (weight- and number-average molecular masses M_W and M_n intrinsic viscosity [η]) and the tacticity of the resulting poly (2,3-epoxypropyl methacrylate)s was investigated. For unfractionated polymers, the constants of the Mark-Houwink equation for 1,4-dioxane and tetrahydrofuran were determined. Gel permeation chromatography was tested as a tool for the determination of the M_w and M_n values.     

Dilute solution properties of poly(methyl methacrylate) in acetonitrile + carbon tetrachloride mixtures

Heterotactic poly(methyl methacrylate) (PMMA) is studied by light scattering and viscometry in the mixture acetonitrile + CCl₄. Both liquids are poor solvents of PMMA, but their mixture is a very good solvent of this polymer. The total sorption potential of the coil is calculated from second virial coefficient and intrinsic viscosity results. Unperturbed dimensions, Mark-Houwink exponent, Schulz-Blaschke constant, and coil expansion factor are also determined. The enhanced total solvent sorption is larger in this mixture than in any other cosolvent system of PMMA thus far studied. This is due to the strong repulsive interactions between acetonitrile and CCl₄. Such interactions also determine the inversion in preferential sorption that occurs close to equimolar composition. Acetonitrile can interact favourably with the ester group of PMMA and unfavourably with its methylene backbone. The role of such opposing interactions and of liquid order in acetonitrile are taken into account to discuss the results.     

Synthesis,dilute solution properties and chain flexibility of poly(diesters) of itaconic acid, 2, poly(methyl decyl itaconate)

The diester of itaconic acid with decyl and methyl groups was prepared and polymerized. The dilute solution behaviour of poly(methyl decyl itaconate) poly{1-(decyloxycarbonylmethyl)-1-(methoxycarbonyl)ethylene} (PMeDI) was studied in tetrahydrofuran and 1-butanol at 298 K, by light scattering, size-exclusion chromatography, and viscometric measurements. The empirical Kuhn-Mark-Houwink-Sakurada relationships were established. The molecular parameters were calculated using one theory of the excluded volume.     

Some solution properties of poly(ethyl methacrylate)

The viscosity of dilute solutions of poly(ethyl methacrylate) in each of methyl acetate, ethyl acetate and isobutyl acetate was studied over the temperature range of 20–65°C. The intrinsic viscosity either remained approximately constant or slightly decreased over the temperature range because of conformational changes. The temperature ranges of conformational change were 40–50°C, 40–50°C, and 35–55°C for the polymer in methyl acetate, ethyl acetate, and isobutyl acetate, respectively. The Huggins constant was also influenced by the type of solvent and by temperature changes, especially over the temperature range in which conformational changes took place. Conformational changes of poly(ethyl methacrylate) in aliphatic organic esters as solvents are believed to be due to changes in the interaction between the polymer segments and the solvent.     

Solution properties of poly(methyl methacrylate) in mixtures of two nonsolvents (carbon tetrachloride and n-alcohols)

Binary mixtures of CCl₄ and several n-alcohols comprise cosolvents for poly(methyl methacrylate). The cosolvency has been explained in terms of the thermodynamic approach of SCOTT and also taking into account some specific effects. In the presence of light a reaction between CCl₄ and alcohol was observed. Unperturbed molecular dimensions determined in the cosolvents agree well with those reported in the literature.     

NMR study of aggregation of heterotactic-like poly(methyl methacrylate) in solution

The aggregation of heterotactic-like poly(methyl methacrylate) (PMMA) in some solutions was proved by NMR spectroscopy. It was found that the fraction of aggregated units depends on solvent, solution concentration and temperature; the aggregates are completely decomposed at 45°C. Aggregation occurs by intermolecular interactions of m-diads with rrr-tetrads, i. e. by interactions of the stereocomplex type. The formation of a stable aggregated structure is probably a consequence of the microstructure of the heterotactic-like PMMA chain, with relatively long sequences of regularly repeating mrrr pentads or mrrr hexads. The aggregation in mixtures of heterotactic-like PMMA solutions with isotactic or syndiotactic PMMA solutions was also studied.     

Synthesis and properties of some poly(methyl)methacrylate stereoisomers

The synthesis of some new stereoisomer poly(methyl methacrylates) is described, and their structure discussed. In the polymerization of methyl methacrylate, initiated by phenyl magnesium bromide and anhydrous cobaltous chloride, polymers with a stereoblock structure are formed. On the basis of NMR spectra, a model can be proposed in which the polymer chains are composed of an isotactic sequency followed by a statistical one. An initiation and propagation mechanism are presented in order to interprete these data. The results of the study of the viscoelastic behaviour of the stereoisomers reported elsewhere are briefly summarized.     

Solution properties and unperturbed dimensions of poly(5-p-methyl methacrylate) and poly(2-tert-butylphenyl methacrylate)

The solution properties of poly(5-p-menthyl methacrylate) and poly(2-tert-butylphenyl methacrylate) are determined by several methods in good and ideal solvents. The flexibilities σ calculated on the basis of the unperturbed dimensions are 3,1 and 2,6, resp. These values are compared with those found for other polymethacrylates with bulky substituents. The influence of a large group in ortho position at the cyclohexyl and the phenyl rings is discussed in terms of steric hindrance and specific interactions.     

The stereoregularity of poly(methyl methacrylate)s formed in the presence of highly syndiotactic poly(methyl methacrylate)s

Methyl methacrylate (MMA) was radically polymerized in the presence of highly syndiotactic deuterated or undeuterated poly(methyl methacrylate)s. In contrast to observations found in the literature no increase in isotacticity was observed. The stereoregularity of the polymers formed in the presence of an undeuterated PMMA as matrix was found by ¹H NMR spectroscopy to be about the same as that in polymers prepared without any matrix, except the polymers formed in the early stage of polymerization which show a little lower syndiotacticity. Determinations of triad tacticities of polymers formed in the presence of deuterated PMMA, gave values of syndiotacticity a little higher than in the case of undeuterated matrixes. The polymer formed in the graft copolymerization of MMA onto pre-irradiated syndiotactic PMMA was fractionated by GPC. The high molecular weight fraction showed a lower syndiotacticity than that of lower molecular weight.     

Solution properties and flexibility of poly(2-biphenylyl methacrylate)

Dilute solution properties of poly(2-biphenylyl methacrylate), (poly[1-(2-biphenylyloxycarbonyl)-1-methylethylene], POB) were studied by viscosity, sedimentation, light scattering and osmotic pressure in different solvents. The solvent dependence of intrinsic viscosity, [η], Huggins constant, K_H, Mark-Houwink exponent, a, and expansion factor, α_η, is very weak, although the chemical nature of the solvents is quite different (CHCl₃, tetrahydrofuran, benzene, 1,4-dioxane). For poly(4-biphenylyl methacrylate) (poly[1-(4-biphenylyloxycarbonyl)-1-methylethylene], PPB) and other aromatic polymethacrylates the changes of [η], K_H, a and a_η are very high. The unperturbed dimensions calculated from viscometric and light scattering data by different methods, are in excellent agreement with one another and good agreement with those obtained from sedimentation data. POB has a higher flexibility factor (σ = 2,8) than PPB (σ = 2,7). In our opinion this is due to the fact that the 2-biphenylyl group is closer to the main chain than the 4-biphenylyl group. The very high value of σ explains the weak solvent dependence of [η], K_H, a and α_η in the case of poly(2-biphenylyl methacrylate).     

Solution properties and unperturbed dimensions of poly(pentachlorophenyl methacrylate)

The properties of dilute solutions of poly(pentachlorophenyl methacrylate) in various solvents are studied by measurements of viscosity and osmotic pressure. The unperturbed dimensions are determined in two Θ-solvents: benzene at 40°C, ethylbenzene at 25°C, and several other solvents such as toluene, chlorobenzene, o-xylene and o-dichlorobenzene at 25°C. The results show a variation of the unperturbed dimensions with the solvent nature in good solvents. The flexibility factor, σ, calculated on the basis on the unperturbed dimensions in a Θ-solvent and the dimensions of a freely rotating chain is higher than that of other polymethacrylates with chlorinated aromatic side groups. The polymer-solvent interactions are discussed in relation to some other polymethacrylates.     

Characterization of the structure of the stereocomplex of poly(methyl methacrylate) in solution from NMR relaxation data

From the values of relaxation times T₂ determined on a pulse spectrometer, and from the shape of bands in high resolution (HR-) and broad line (BL-) NMR spectra, two types of protons, different in mobility, were found to exist in the associated stereocomplex of isotactic (it-) and syndiotactic (st-) poly(methyl methacrylate) (PMMA). From the analysis of NMR spectra, measured at magic angle rotation (MAR-NMR), the mobility of the ester groups in the stereocomplex is shown to be greatly hindered. Temperature changes of HR-NMR spectra of mixed solutions of it- and st-PMMA in benzene indicate that the associated segments of the stereocomplex can be characterized as junctions of a network of nonassociated sequences.     

Solution properties of ultrahigh-molecular-weight polymers, 16. Unperturbed dimensions of poly(isobutyl methacrylate)

Three techniques, i. e., the Lenka extrapolation method, the Stockmayer-Fixman method, and the extrapolation of the Mark-Houwink constants to a = 0,5 were applied to determine the unperturbed dimensions of ultrahigh-molecular-weight poly(isobutyl methacrylate). A correction term, depending on the exponent a of the Mark-Houwink relation, is suggested to be introduced into the Stockmayer-Fixman-Burchard equation.