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Chain dimension of polystyrenes diluted with low molecular-weight homologues in semi-dilute solutions was investigated, referring to the results for solutions in benzene and styrene monomer, and its concentration dependence was clarified by small-angle neutron scattering (SANS) with a “contrast-matching” method. The styrene monomer was found to act as a good solvent comparable to benzene. The polystyrene was confirmed to expand in the bulk “diluent” homologues having sufficiently low molecular-weights, and its concentration dependence of expansion factor, α, became weaker with increasing the degree of polymerization, NS, of the short “diluent” polymer. The critical NS value, NS,c, which is defined as the maximum value to give excluded volume effects, was much higher than the earlier theoretical prediction by de Gennes, i.e., N S , c ∼ N L 1 / 2 , where NL is the degree of polymerization of the long “solute” polymer. The power law exponent for NS-dependence of α seems to follow −1/16, rather than −1/8 predicted by the scaling, suggesting that screening blob size, ξ, can be scaled as ξ ∼ N S 1 / 2 , which is equivalent to the radius of gyration for the “diluent” polymers.

Poly(2-vinylpyridine) (P2VP) with cyclic structure was tentatively prepared through the reaction of linear P2VP having two living ends followed by coupling with a bifunctional coupling agent. Thus, prepared crude product was fractionated by preparative size exclusion chromatography in order to enrich the cyclic polymer portion. Then the existence of the ring structure in the fractionated P2VP sample was directly confirmed for the first time by pyrolysis−gas chromatography/mass spectrometry by detecting the characteristic fragments reflecting the coupling moiety of the polymers at which the coupling agent combined the living 2VP units at both functional points.

13 C NMR Relaxation of iso-Poly(2-vinylpyridinium chloride) in Aqueous Solution. Effects of Electrostatic Interactions on Local Chain Dynamics

The steady shear rate dependence of the structure of two poly(styrene-d8-b-2-vinylpyridine)s in α-chloronaphthalene, a common good solvent, was measured by small-angle neutron scattering (SANS) in a couette flow cell geometry in the ordered state, in which the solutions assume a lamellar structure (randomly oriented grains). SANS measurements revealed that steady shear flow induces macroscopic lamellar orientation at certain characteristic shear rates for the higher molecular weight sample (M w = 3.6 × 10 5 ). Lamellar normals are preferentially oriented along the vorticity direction at high shear rates. However, no shear effect was observed for the low molecular weight sample (M w = 2.0 × 10 5 ).

We examined chain degradation in rheological measurements and the effects of molecular weight distributions (MWDs) on rheological data at steady states for polystyrenes in dioctyl phthalate undergoing flow-induced phase separation. The chain degradation occurred when we observed a strong overshoot in transient stresses. The suppression of overshoot by lowering the concentration and the molecular weights of the samples, and/or by making a step increase in the shear rate, was effective in preventing the degradation. The most significant difference between the rheological data for samples with broad and narrow MWDs is the existence of plateau in the first normal stress difference in the former. Shear rate dependences of the stresses of broad MWD samples in the shear rate range before the plateau are somewhat steeper than those of narrow MWD samples.

Lamellar domain spacings (D) of blends of a styrene-2-vinylpyridine (SP) diblock copolymer and homopolymers corresponding to the block polymers (S and/or P), of which molecular weights are lower than that of the block polymer, were examined by small-angle X-ray scattering (SAXS), and the dimensions of block chains in the lamellae were investigated by small-angle neutron scattering (SANS). The D's for SP/S/P ternary and SP/S (or SP/P) binary blends increase with increasing the molecular weight of the homopolymers, MH, as well as the volume fraction of the homopolymers, ΦH, in the corresponding lamella. The variations of the D's with ΦH for the blends with homopolymers having different MH's reveal that homopolymers with higher MH are localized at the center of the corresponding lamella, while those with lower MH are distributed throughout the lamella. Moreover, the comparison between the D's for ternary and binary blends with homopolymers having equal MH's implies that the homopolymers in binary blends are ...

Segment distribution of styrene in an alternating lamellar structure of styrene−2-vinylpyridine diblock copolymer was investigated by neutron reflection. Block copolymers having three types of deuterium-labeled styrene block chains consisting of fully labeled, partially junction-labeled, and partially end-labeled block chains were used in this study. The degree of junction and end labeling was varied to obtain a more complete picture of segment distribution. Spin-coated thin films of these block copolymers on silicon wafers exhibited lamellar structures which were oriented preferentially parallel to the silicon surface. Our results indicate that the poly(2-vinylpyridine) block chain exists at the silicon surface, while polystyrene appears at the air surface in all of the film specimens. The segment distribution at the interface between polystyrene and poly(2-vinylpyridine) lamellae could be well described by an error function. The thickness of the lamellar interface (defined as a full-width half-maximum v...

The molecular weight dependence of lamellar domain spacing of poly(2-vinylpyridine-g-styrene) was measured by small angle X-ray scattering (SAXS). The samples used are six three-arm star-shaped polymers having one polystyrene arm connected at the centre of a poly(2-vinylpyridine) chain. The volume fractions of grafted polystyrene chains, ƒ s , of the samples range from 0.45 to 0.78, though all the samples were confirmed to have alternating lamellar structure by SAXS and transmission electron microscopy. It was found that the relationship between lamellar domain spading, D, and the molecular weight, M, of the graft copolymers is given by D = 0.0153 M0.69 (nm) over the molecular weight range from 49 to 283 k irrespective of the difference in composition. The exponent 0.69 is quite close to 2 3 , which is predicted for AB diblock copolymers by several different theories. However, the magnitude of the prefactor in the above relationship is apparently smaller than that for styrene-2-vinylpyridine diblock copolymers. This difference can be explained by considering the difference in structure between AB diblock copolymers and ABB graft copolymers.

Viscoelastic properties of non-entangled concentrated aqueous solutions of three sodium polystyrenesulfonates with low molecular weights were measured in oscillation flows. Master curves of dynamic moduli were obtained by shifting the moduli data measured at different concentrations along the frequency (ω) axis for each molecular weight. The concentration shift factor used in making the master curves composes a single line irrespective of molecular weight. Storage and loss moduli are proportional to ω 2 and ω, respectively, in the terminal region, while they are proportional to ω 1/2 in the transition region. All the master curves can be well represented by the modified Rouse theory using the experimental values of concentration, molecular weight and viscosity in a reference state.

We prepared well-defined styrene (S)-2-vinyl-pyridine (P) graft copolymers of the ABB type or SPP graft copolymers, in which as block chain is grafted at the center of a block chain, as a model graft copolymer by anionic polymerization and coupling reaction. The composition dependence of morphology of SPP graft copolymers is qualitatively the same as that of SP diblock copolymers, but the composition range of each structure is shifted to the higher volume fraction of S block chain. The molecular weight dependence of lamellar domain size of SPP graft copolymers is almost the same as that of SP diblock copolymers, but the magnitudes are smaller. These experimental results are well explained by the difference in chain architectures.

Poly(2-vinylpyridine-g-styrene)s were prepared by successive coupling reactions of polystyryl anion and poly-2-vinylpyridinyl anion prepared by anionic polymerizations, with trifunctional coupling agent, tris-bromomethylbenzene. Five samples were prepared and characterized. Their volume fractions of polystyrene graft,os, were determined to be 0.24, 0.34, 0.45, 0.58 and 0.67, respectively. Morphologies of the solvent-cast films of the samples were observed by transmission electron microscopy and small-angle X-ray scattering. It was revealed that two samples, with os of 0.24 and 0.34, show cylindrical structures, while the other three samples have alternating lamellar structures.

Alternating lamellar structures of poly(2-vinylpyridine-b-styrene-b-2-vinylpyridine) triblock copolymers of the ABA type with different compositions were studied by transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), and small-angle neutron scattering (SANS). The volume fractions of polystyrene (S), Φ s , of the copolymers range from 0.28 to 0.58, whereas the chain lengths of two end block polymers, poly(2-vinylpyridine) (P), are always the same for each sample. It was confirmed that all the solvent-cast films had alternating lamellar structures, and the measured microdomain spacings were in good agreement with the theoretical prediction by Helfand and Wasserman irrespective of the compositions. SANS studies revealed that the middle block polymers (S) are elongated along the direction normal to the lamellar interface, but they are shrunk along the direction parallel to the interface, so that the volume occupied by the middle block polymers are the same as those in the unperturbed states, and the degree of deformation decreases with increasing Φ s .

Viscoelastic properties of homogeneous polystyrene/poly(vinyl methyl ether) (PS/PVME) blends were studied in terms of the zero-shear viscosity η 0 and the steady-state compliance J e . The molecular weight and composition of PS (M PS and O PS ) were varied, whereas the molecular weight of PVME (M PVME ) was fixed, maintaining the condition M PS »M PVME . The behavior of η 0 and J e was discussed as a function of M PS and O PS

Four types of morphology, lamellar, ordered tricontinuous double-diamond (OTDD), cylindrical, and spherical structures, of isoprene (I)-styrene (S)-2-vinylpyridine (P) triblock copolymers having I and P block polymers with the same volume fractions, were studied by TEM and SAXS. These studies revealed that the spherical structure has the packing manner of the CsCl type consisting of two spherical domains of I and P end-block polymers and the cylindrical structure, which consists of two kinds of cylindrical domains of end-block polymers, has the tetragonally-coarrayed pattern

Viscoelastic properties of polystyrene/poly(vinyl methyl ether) blends with nearly critical compositions were measured under steady-shear flows near the phase separation temperatures. In the homogeneous region, shear rate dependences of shear viscosity J S and shear compliance J S are practically the same as those of homopolymers. In the phase-separated region at quiescence, on the other hand, η and J S are enbanced at low shear rates, but they become almost the same as those in the homogeneous region when the shear rates are higher than their respective critical shear rates. The critical shear rate values from J S , γ cJ , were found to be larger than those from η, γ cV , and γ cJ , is considered to be almost equal to the critical shear rate for shear-induced homogenization γ c

Single-chain conformations of styrene homopolymers dissolved in a polystyrene lamellar microdomain of a styrene-2-vinylpyridine diblock copolymer in but were measured by SANS. The molecular weights of the styrene homopolymers are 13.0K (L), 29.7K (M), and 76.7K (H), and the molecular weight of the diblock copolymer is 63.3K with 34.2K of polystyrene block. The mixing ratios of homopolymer/block copolymer blends are 0.1/0.9 for L, 0.05/0.95 for M, and 0.01/0.99 for H so as not to give rise to macrophase separation. The radii of gyration of homopolymers in the direction parallel to the lamellae are found to be almost equal to the unperturbed dimension irrespective of the molecular weight ratios of homopolymers to the polystyrene block

Viscoelastic properties of a polystyrene-poly(vinyl methyl ether) blend were measured in oscillatory and steady shear flows near the phase separation temperature. In the one-phase region, the viscoelastic properties are independent of the type of flow and flow geometry, and their shear and frequency dependences are the same as those of homopolymers. When phase separation occurred, a change in viscoelastic properties was observed in all types of flow and flow geometries, and they are different in the different types of flow and/or different flow geometries in the two-phase region. In the shear rate dependence of viscosity of the polymer blend in the two-phase region at quiescence, a plateau region was observed, in which the shear viscosity can be regarded as the zero shear viscosity of the homogenized polymer blend at that temperature.

Styrene(S)-isoprene (I) star-shaped block copolymers of the (SI)4 and (SI)12 types were prepared by an anionic polymerization technique. Linear SI arm molecules were prepared with sec-butyllithium as an initiator in benzene, followed by a coupling reaction with the 4-functional linking agent 1,2-bis(methyl-dichlorosilyl)ethane and the 12-functional 1,1,2,2-tetrakis(2-(trichlorosilyl)ethyl)silane, respectively, under vacuum. The star-shaped block copolymers were isolated by precipitational fractionation from aspolymerized crude products using benzene-methanol mixtures. They were confirmed to have the designed molecular structures by careful characterization. Using a transmission electron microscope it was observed that the microphase-separated structures of solvent-cast films of the samples are polystyrene (PS) cylinders in a polyisoprene (PI) matrix, alternating lamellar structures and PI cylinders in a PS matrix for 4-armed star-shaped block copolymers when the values of the volume fraction of PS, ф s , are 0.23, 0.47 and 0.78, respectively, and lamellar structures for the 12-armed star-shaped block copolymers when the ф s values are ∼0.5. Small-angle X-ray scattering studies revealed that lamellar domain spacings of the star-shaped block copolymers are essentially the same as those of the arm molecules, that is, linear diblock copolymers, irrespective of the number of arms.

Styrene(S)-isoprene(I) multiblock copolymers of the (SI)n type (n = 1, 2, 3, 4) were prepared by a multistep monomer addition technique of anionic polymerization. Molecular weights of SI diblock units are almost the same and the total polystyrene volume fractions are about 0.5. All the film specimens cast from toluene solutions were found to have alternating lamellar structures. The lamellar domain spacing monotonically decreases and approaches an asymptotic value with increasing the number of blocks.

The localization of deuterated styrene homopolymer dissolved in a lamellar structure of a styrene-2-vinylpyridine diblock copolymer was studied in comparison with that of the end part of the block copolymer by observing diffraction from the styrene and 2-vinylpyridine microdomains of deuterated styrene homopolymer/styrene-2-vinylpyridine diblock copolymer blends by SANS. From the diffraction profiles in SANS and the dependence of domain spacing on the volume fraction of the styrene homopolymer, it was found that the homopolymers are isolated in the middle of the polystyrene domain, though they are concentrated less than the end parts of the block chains

The molecular weight dependence of the lamellar domain spacing of isopren-styrene-2-vinylpyridine triblock copolymers in bulk was studied over the molecular weight range from 40K to 280K by using SAXS. It was found that the lamellar domain spacings of the triblock copolymers are larger than those of styrene-2-vinylpyridine diblock copolymers with the same molecular volumes. This result can be interpreted by theories of microphase separation at the strong segregation limit, taking into account the fact that the number of boundaries in the repeating structure of triblock copolymers is twice as large as that of diblock copolymers

The fluorescence anisotropy decay method is used to measure the rotational diffusion of 9,10-diphenylanthracene and the segmental motion of anthracene-labelled polystyrene in tetrahydrofuran solutions of polystyrene. The concentration dependences of these two measures of microscopic friction are reported from pure solvent to 70% polymer at 4.5, 25.0 and 45.5°C. These results are compared to previously reported measurements of the translational diffusion of methyl red in the same system, and to the temperature dependence of the solution viscosity of a closely related system. The three measures of microscopic friction show similar concentration dependences.

A complicated three-dimensional equilibrium morphology, named an ordered tricontinous double-diamond (OTDD) structure, similar to the ordered bicontinous double-diamond structure for diblock copolymers was found for the microphase-separated structure of poly(isoprene-b-2-vinylpyridine). When the contnets of both end-block polymers are equal, this structure occurs from 0.48 to 0.66 for the volume fractions of middle-block polymer, i.e., polystyrene. The TEM data at the two different directions, i.e. the [111] and [001] directions are in good agreement with the corresponding images formed by assuming the OTDD structure proposed

The variation of morphology of triblock copolymers of the ABC type, poly(isoprene-b-styrene-b-2-vinylpyridine), with comparition was studied by TEM. Four types of morphology were observed for the microphase-separated structures of the samples whole volume fractions of the middle-block, polymer, polystyrene, range from 0.3 to 0.8, while keeping the volume fractions of the end-block polymers, i.e., polyisoprene and poly(2-vinylpyridine), equal. They are a three phase four-layer lamellar structure, an ordered tricontinuous double-diamond structure, a cylindrical structure and a spherical structure

Steady-state compliance J e of poly(N-methyl-2-vinylpyridinium chloride) solutions was measured in the absence and presence of added salt. In dilute regions, J e depends on molecular weight M, polymer concentration C and added salt concentration C s . The M and C depenences are much stronger than that of non ionic polymers as given by J e ∞ M -2 C -3 C s . In entangled regions, J e depends on C only in the same manner as for that of nonionic polymers solutions, but the concentration dependence is weaker than that of nonionic polymers as given by J e ∞ C - 1 .3

Chain dimensions of the polystyrene-d8 parts of a styrene-d8-2-vinylpyridine block copolymer (DP-33) and a styrene-d8-styrene-h8 block copolymer (DH-44), both with 50:50 compositions, were measured in dilute solutions of pyridine (a common good solvent) benzene (a selective solvent) and methyl ethyl ketone (a poor solvent) by small-angle neutron scattering. The conformation of one block chain within a diblock copolymer is not affected by the existence of another block chain, regardless of the solvent power at least when the composition of the diblock copolymer is 50:50, and the molecular weight is not high.

Zero-shear viscosity η 0 of solutions of poly(N-methyl-2-vinylpyridinium chloride) having molecular weights M w of 6.94x10 5 , 1.10x10 6 and 2.73x10 6 was measured in the absence and presence of added salt. It was found that the polymer concentration dependence of η 0 in semidilute regions increases with increasing salt concentration and almost agrees with that for nonionic polymers in good solvents at high concentrations of added salt.

Diblock copolymers of styrene and 2-vinylpyridine studied by SAXS and SAWS. It is found that the chain adjacent to the junction between the two blocks is located near the boundary between domains and is contracted along the direction parallel to the lamellae to the same extent as a whole block chain with the same molecular weight, while the chain at the free end of block polymer is located in the middle of domain and is unperturbed

The radii of gyration of a polystyrene block along the directions parallel and perpendicular to the lamellae in the lamellar structure of poly(styrene-b-2-vinylpyridine) were measured by SANS. It was found that the block polymer is extended along the perpendicular direction, while it is contracted along the parallel direction. It is suggested that the block polymer is contracted along the parallel direction to keep the volume occupied by the block chain constant when the microphase separation occurs

Styrene/2-vinylpyridine diblock copolymers are studied by SAXS. It was found that the lamellar domain spacing-molecular weight relationship of the diblock copolymer in bulk is given by D=0.33 7 M 0.64 over the molecular weight range from 38 K to 740 K. The experimental result is in good agreement with the theories on the basis of Gaussian chain statistics in a confined space, particularly the theory of Helfand-Wasserman

The longest relaxation times τ m of linear PS in concentration regions between the critical concentrations for the zero-shear viscosity η 0 and for the steady-state compliance J e , were studied by measuring the stress relaxation after cessation of steady shear flow. It is concluded that the weight-average relaxation time τ w (=η 0 J e ) is well represented by τ m and the magnitudes of the contribution of the terminal relaxation processes to η 0 are the same in semidilute solutions for η 0 , whether the entanglements are effective to J e or not

Viscoelastic properties of poly(isoprene-b-styrene) in dioctylphthalate under steady shear flow were measured near the order—disorder transition temperature. In ordered states, first normal stress difference N1 is proportional to shear rate γ at low γ region, but becomes proportional to γ 2 at the high γ region, similar to the N1 behaviour of polymer blends undergoing shear-induced homogenization. Because the existence of microdomains was confirmed at the high γ region by the flow birefringence method, it is concluded that the above N1 behaviour is not caused by shear-induced homogenization, but is probably caused by the shear-induced alignment of the microdomain structure.

Flexibilite de la chaine de poly t-butyl crotonate par diffusion RX aux petits angles. Comparaison avec le polyacrylate de «t»-butyle, le polymethacrylate de «t»-butyle et le polycrotonate de sodium

Published theoretical equations for the sedimentation coefficient and intrinsic viscosity of a semiflexible chain are compared, neglecting the excluded volume effect. The theories are extended to the case of a small excluded volume, by applying the perturbation theory, established for flexible chains, to a semiflexible chain. Using the derived equation, the experimental results for the sedimentation coefficient and intrinsic viscosity of DNA and cellulose trinitrate are analyzed.

Determination de la pression osmotique de solutions concentrees de polystyrenes de differentes masses moleculaires dans des bores solvants, par mesure de la pression de vapeur

To study the expansion process of bovine plasma albumin in acidic solutions, observed potentiometric titration curves at three different ionic strengths were compared with theoretical curves, using the radii of the protein determined by small angle X-ray scattering (SAXS). From the comparison, it was concluded that the expansion is completed via two different transitions and that the conformation of the protein before the first transition is stable and common at all ionic strengths, whereas the form of the protein becomes a more swollen and unstable one after the first transition. Moreover, the charge-independent part of the standard free energy change, delta G0, in the first transition was estimated from the potentiometric titration curves. The numerical value of delta G0 is 2350 +/- 50 cal/mol, which is very small compared with the corresponding one for ordinary biopolymers.

Rayon de giration de sections marquees au deuterium de polystyrene de distribution etroite de masse moleculaire en solution dans le disulfure de carbone

Solutions de poly(α-methystyrene) dans des solvants bons, pauvres ou theta. Theorie de Gennes applicable en regime semidilue mais pas si la concentration du polymere est superieure a 0,2 g/mL