Dilute solution properties of critically branched systems

Light-scattering measurements were carried out on critically branched polycondensates of 1,3,5-benzenetriacetic acid and 1,10-decanediol, and the results were analysed according to the theory of cascade processes, developed especially for this system, viz. the pathweighting generating function method. It is postulated that the amount of chain expansion found in these branched copolycondensate samples was due to short-range rather than long-range interactions. The long-range interactions seem to vanish in the critically branched state. The rotational isomeric state model was used to calculate the comparative unperturbed dimensions for the linear homologue of the above polycondensate, i.e. poly(1,3-benzenediacetic acid/1,10-decanediol).     

Dilute solution properties of poly(m-methyl styrene)

Viscometric and osmometric studies have been carried out with fractions of poly(mmethyl styrene) in solutions of benzene, cyclohexane, and ethyl acetate at 30, 40, and 50°C. The values of K′ and ‘a’ in the KUHN-HOUWINK relation have been reported for the above polymer-solvent systems. The values of unperturbed dimension, (r /M)^1/2, solvent polymer interaction constant (B) and conformational parameter (σ) have been computed applying the theories of FLORY-FOX-SCHAEFGEN, KURATA-STOCKMAYER-ROIG, and STOCK-MAYER-FIXMAN. The applicability of the theories of FLORY, KURATA et al., and PTITSYN has been critically analysed from the dependence of the expansion factor (α) on molecular weight. Values of thermodynamic parameters, Θ, Ψ₁, x₁, and X₁, have also been calculated.     

Dilute solution properties of poly(propylene oxide)

We prepared poly(propylene oxide) using an aluminum isopropoxide-zine chloride catalyst system at a temperature of 70-80°C for seven days. This procedure heavily favored the production of isotactic^1,2 material. We separated the isotactic portion from the atactic using acetone at ?30 to ?70°C. The isotactic material was fractionated at 70°C with the system isopropanol/water. The atactic material degraded during fractionation and was not used in this work. For the isotactic polymer relationships were found between M_n and [-η], M_n and A_n, and [η] and A_n. The differential thermograms showed a melting point of 62 ± 1°C and gave no evidence of an exotherm up to 300°C under a nitrogen atmosphere. The polymer degraded in air and various polar solvents. However, non-polar solvents did not have this effect, and were used for the various determinations.     

Dilute solution properties and unperturbed dimensions of poly(di-ni-alkyl itaconate)s

The diesters of itaconic acid (methylenesuccinic acid) with higher C₁₂ – C₂₀ unbranched, saturated, aliphatic alcohols were prepared, purified, and polymerized in bulk or in solution with 2,2′-azoisobutyronitrile as initiator. The transparent to waxy polymers obtained were fractionated and all fractions characterized by viscosity and light scattering measurements. The Kuhn-Mark-Houwink-Sakurada relations were established and then extrapolated to thetaconditions, in order to calculate the unperturbed dimensions. High values of the steric factor σ, and the characteristic ratio C_∞ were obtained. The results correlate well with those obtained previously for poly(di-n-alkyl itaconate)s from the corresponding lower C₁ – C₁₁ alcohols.     

Dilute solution properties of polybutadiene modified by 4-phenyl-1,2,4-triazoline-3,5-dione

The dilute solution properties of 4-phenyl-1,2,4-triazoline-3,5-dione-modified polybutadienes were studied in tetrahydrofuran by static and dynamic light scattering and compared with those from unmodified polybutadiene chains. For the unmodified polymer, the scaling laws were established and the coil interpenetration parameter k was determined in the thermodynamically good solvent tetrahydrofuran; the chains exhibited common flexible chain behavior. For the modified polybutadiene, the results indicate at infinite dilution a weak extent of intermolecular crosslinking via the urazole groups, coupled with a very high extent of intramolecular ring formation. In order to evaluate the fraction of rings, an analysis of the association equilibrium by Fourier-transform infrared spectroscopy (FTIR) was performed in the absorption region of the carbonyl stretching vibration of the urazole ring.     

Dilute solution properties of poly(allylammonium chloride) in aqueous sodium chloride solutions

Ten fractions of poly(allylammonium chloride) were investigated at 25°C in sodium chloride solutions of various concentrations, c_s, by viscosity and light scattering techniques. The molecular weight (M_w)-intrinsic viscosity [η] relationships were established at four NaCl concentrations. The unperturbed dimensions estimated from the Stockmayer-Fixman plot are independent of c_s. The second virial coefficient A₂ and the excluded volume parameter B as well as [η] were found to be proportional to c and to have negative values in the limit of infinite c_s. In addition, it was found that the electrostatic part of the expansion factor can be expressed in terms of a reduced parameter (M_w/c_s)^1/2 in a fairly wide range of M_w and c_s.     

Dilute solution properties of methyl methacrylate/acrylonitrile random copolymers, 1. Mark-Houwink relation

Studies on the dilute solution properties of methyl methacrylate/acrylonitrile random copolymers of 0,566 mole fraction (m. f.) of acrylonitrile (AN), designated as MA3 and of 0,657 m. f. of AN, designated as MA4 reveal that the Mark-Houwink exponent values a for MA3 lie in the range 0,6 to 0,8 and for MA4 in the range 0,8 to 1,1 in the solvents studied, viz. acetonitrile (MeCN), 2-butanone (MEK), N,N-dimethylformamide (DMF) and γ-butyrolactone (γ-BL) at the temperatures 30°C, 45°C and 60°C. Such large values of a suggest that these copolymer chains are highly extended in these solvents. The decrease of [η] with an increase in temperature also supports the above conclusion that these are very good solvents.     

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.     

Lyotropic mesophase of imogolite, 2. Microscopic observation of imogolite mesophase

Imogolite, though achiral, forms cholesteric spherulites in the anisotropic phase as shown by the regular striations arranged in a swirl-like or fingerprint pattern observed through a polarizing microscope. Electron microscopy revealed the raft-like imogolite sheet floating in the anisotropic phase. The structure of the imogolite sheet was deduced from periodicities observed by an electron microscope using various imaging conditions. The origin of the twisting force to maintain the cholesteric ordering is also discussed.     

Dilute solution properties of methyl methacrylate/acrylonitrile random copolymers, 2. Stockmayer fixman relations

The Stockmayer-Fixman relation was used to evaluate the short range and long range interaction parameters for methyl methacrylate/acrylonitrile copolymers of 0,566 and 0,657 mole fraction of monomeric units of acrylonitrile in the solvents acetonitrile, 2-butanone, dimethyl formamide, and γ-butyrolactone, at different temperatures (30, 45, and 60°C). The values of K₀ were found to be lower than those of the parent homopolymers, and their values depend on both solvent and temperature. Even negative K₀-values were obtained, in cases in which the Mark Houwink exponent a is nearly unity. The values of the polymer-solvent interaction parameter, χ₁, are high and close to 0,5, indicating that these solvents are not good. The values of the excess interaction parameter, χ_AB, are negative and are not affected by temperature. The large extension of these copolymer chains, as exhibited by a and α-values, can be understood in terms of unusual short range interactions only. Similar results were obtained for some cellulose derivatives.     

Dilute solution properties of well-defined multiblock copolymers: poly(4,4′-isopropylidenediphenyl carbonate)-block-polystyrene

Light scattering, osmometric and viscometric studies were carried out with dilute solutions of well-defined poly(4,4′-isopropylidenediphenyl carbonate)-block-polystyrene multiblock copolymers, PC-b-PS, in non-selective and selective solvent systems. The influence of copolymer composition, numbers and lengths of blocks in the copolymer chain and type of solvent used on the dilute solution properties, conformation of the investigated multiblock copolymers and on some thermodynamic parameters are discussed. The intrinsic viscosity [η], the unperturbed dimension 〈R₀²〉/M and the second virial coefficient A₂ are larger in non-selective solvents than expected from the averaged values of the parent homopolymers. In benzene, a selective solvent for polystyrene, formation of micelles is possible.     

Dilute solution properties of alternating copolymers from methacrylonitrile and styrene and methacrylonitrile and α-methylstyrene

Kuhn-Mark-Houwink-Sakurada relations were obtained in various solvents for alternating copolymers from methacrylonitrile and styrene, (MAN-ST), and from methacrylonitrile and α-methylstyrene, (MAN-αMST). The values of the unperturbed dimensions, Kθ or A=(r /M)^1/2 and conformational parameter σ were determined using usual extrapolation techniques. The values of the unperturbed dimensions are dependent on the solvent nature and are quite different from the “ideal” values calculated on the basis of additivity rules from the unperturbed dimensions of the parent homopolymers.     

Dilute solution properties of high molecular weight poly(isobutyl methacrylate). III. Effect of centrifuging on various parameters

Three high molecular weight samples of poly(isobutyl methacrylate(designated as 937, SW 63/0082, and SW 62/0298 were obtained from Edgewood Arsenal, Maryland. Sample 937 has been fractionated and described^l,2) earlier. Initial investigations have shown that the solution viscosities were shear dependent. The three samples were subjected to centrifugation at constant velocity for various times. The intrinsic viscosity and molecular weight (M?_w) dropped slightly for sample 937, but dropped drastically for the other two samples. The number average molecular weight (M?_n) remained constant for each sample under these conditions. In this presentation we have also shown the necessity for taking measurements at low angles daring light scattering measurements in order to obtain the correct molecular weight (M?_w) for these high molecular weight species.     

Polymer solutions XII. Dilute solution behaviour of randomly branched polyvinyl acetate

Dilute solution behaviour of randomly branched polyvinyl acetate fractions has been examined by viscosity, osmotic pressure and light scattering techniques. The weight- to number-average mol. wt. ratios obtained are very high, indicating that the fractions have very broad mol. wt. distributions. The ordinate [η]_R, at the common point of convergence of the various In η_r/c vs. c plots for the same polymer in different solvents correlates well with the square-root of the viscosity-average mol. wt. obtained using the logarithmic normal distribution of WESSLAU. The branching parameters obtained are higher in poor solvents than in good solvents, indicating that the branched molecules are less expanded over their unperturbed dimensions as compared to linear molecules of the same mol. wt. The chain transfer constant C_p for the polymer gives estimates of branching in agreement to those obtained from measured dimensions. Reliable estimates of branching are obtained from [η]_R using the ZIMM-THURMOND relationship at lower branching frequencies and the ZIMM-KILB relationship at higher branching frequencies.     

Hydrophobic water-soluble polymers, 1. Dilute solution properties of poly(1-vinyl-2-piperidone) and poly(N-vinylcaprolactam)

Poly(vinyllactams) form a class of non-ionic water-soluble polymers from which only poly-(1-vinyl-2-pyrrolidone) (PVP) is well known and has been investigated extensively. The homologues poly(1-vinyl-2-piperidone) ( 1 , poly[1-(2-oxo-1-piperidyl)ethylene]) and poly(N-vinylcaprolactam) ( 2 , poly[1-(2-oxoperhydroazepin-1-yl)ethylene]) which are still soluble in water at room temperature have not yet been studied in aqueous solution. In this work the synthesis of these two polymers by radical polymerization in solution and the investigation of the dilute aqueous solution properties of these polymers by static and dynamic light scattering measurements are presented. Special attention is paid to the influence of the increasing hydrophobicity of these polymers on coil dimensions and structures in aqueous solution.     

The solution properties of poly-o-chlorostyrene

The solution properties of poly-o-chlorostyrene in toluene were measured by means of light-scattering and viscosity method, and the results were compared with those obtained from other polystyrene derivatives. The dependence of the intrinsic viscosity, the second virial coefficient and the end-to-end distance of the polymer chain on the molecular weight is follows: These relationships do not differ substantially from those of other polystyrene derivatives. The unperturbed dimension of poly-o-chlorostyrene was calculated. Results showed that the polymer chain of poly-o-chlorostyrene at the theta state, {<L²>o/<L²>_f}^1/2 = 2.42, was more extended than that of poly-p-chlorostyrene, {<L²>o/<L²>_f}^1/2 = 2.15 to 2.30.     

Lyotropic mesophase of imogolite, 1. Effect of polydispersity on phase diagram

The acidic aqueous solution of imogolite is proposed to be an ideal lyotropic system. No temperature dependence was marked on the two phase boundary concentrations (A and B points) of imogolite solutions as predicted by the theories of Flory and Onsager. A satisfactory quantitative agreement was observed with Onsager's theory. The polydispersity of rod lengths was found to shift the A point towards lower concentrations than expected from theory.