Structure investigation of poly((2-dimethylamino)ethyl methacrylate)/sodium dodecylsulfate complexes in concentrated poly((2-dimethylamino)ethyl methacrylate) solutions using small angle neutron scattering

The structure of poly((2-dimethylamino)ethyl methacrylate)/sodium dodecylsulfate complexes in water was investigated as a function of poly((2-dimethylamino)ethyl methacrylate) concentration at a fixed sodium dodecylsulfate concentration using small angle neutron scattering. When either hydrogenated or deuterated sodium dodecylsulfate was added to poly((2-dimethylamino)ethyl methacrylate) solutions in D₂O, a peak was observed in the small angle neutron scattering which was characteristic of charged micelles. This peak shifted to higher q in both cases as poly((2-dimethylamino)ethyl methacrylate) concentration increased, indicating that the size and shape of micelles changed due to favorable interactions between poly((2-dimethylamino)ethyl methacrylate) and sodium dodecylsulfate. The small angle neutron scattering intensity of the micelles in the polymer/surfactant solutions was measured at the condition where poly((2-dimethylamino)ethyl methacrylate) was contrast-matched. It was possible to obtain information about the structure of the micelles using the Hayter–Penfold model. Based on the results from the fit of the SANS data, it was found that partial shielding provided by poly((2-dimethylamino)ethyl methacrylate) monomers being incorporated into the micelle shell significantly influenced both the form factor and the structure factor of micelles in the polymer/surfactant solutions. This led to a decrease in the micelle size and an increase in the number of micelles. It was found that any increased repulsive potential resulting from a smaller distance between the charged micelles was relieved by a decrease in the surface charge.     

On the deformation of poly(methyl methacrylate) poly(ethylene oxide) blends: A molecular characterization by small-angle neutron scattering

The deformation behavior of miscible amorphous/amorphous PMMA/PEO poly(methyl methacrylate)/poly(ethylene oxide) blends was compared with that of pure PMMA. Small-angle neutron scattering experiments were performed on labeled systems made of PEO + D-PMMA + HPMMA. Characteristic molecular parameters such as radius of gyration, Rg, molecular weight, M_w, and interaction parameter, X, were extracted from the coherent scattering cross sections, Molecular anisotropy was measured on the solid state coextruded samples, and the observed drawing efficiency is compared with, the results of shrinkage tests. In the case of PMMA/PEO blends, anomalous scattering behavior precludes any quantitative Interpretation of the scattering patterns, but revealed important structural changes upon drawing, namely a deformation-induced phase separation.     

Small angle neutron scattering study of deuterated sodium dodecylsulfate micellization in dilute poly((2-dimethylamino)ethyl methacrylate) solutions

Poly((2-dimethylamino)ethyl methacrylate) with 60,000 g/mol and a narrow polydispersity (1.12) was synthesized using group transfer polymerization in order to investigate the structure of poly((2-dimethylamino)ethyl methacrylate)/sodium dodecylsufate complexes in water. The synthesized polymer chain conformation in water was studied as a function of deuterated sodium dodecylsulfate concentration using small angle neutron scattering. We found three transitions of the poly((2-dimethylamino)ethyl methacrylate) chain conformation induced by the added deuterated sodium dodecylsulfate. The transitions resulted from interactions between the polymer and the surfactant, so that micelles are formed along the polymer backbone above the critical aggregation concentration. The structure of micelles in a poly((2-dimethylamino)ethyl methacrylate)/deuterated sodium dodecylsulfate solution was analyzed through model fitting of the small angle neutron scattering data measured at the condition where the poly((2-dimethylamino)ethyl methacrylate) was contrast-matched with a mixture of 80% H₂O and 20% D₂O.     

Diffusion of hairy polymeric micelles in a homopolymer solution

Polystyrene-block-poly(4-vinylpyridine) (PS-b-PVP) forms hairy micelles with PVP and long PS block as the core and corona in toluene, respectively. Diffusion of the micelles in solution in the presence of poly(methyl methacrylate) (PMMA) or polystyrene homopolymer (h-PS), from dilute to semidilute, has been investigated by laser light scattering (LLS). Our results indicate the micelles only exhibit translational diffusion with characteristic Γ = Dq² in PMMA dilute and semidilute solutions, where Γ, D and q are characteristic line width, translational diffusion coefficient and scattering vector, respectively. PMMA concentration dependence of D reveals that the micelle diffusion follows a “stretched exponential” scaling law, similar to that of a hard sphere in the presence of matrix polymer. This is because the PS corona is incompatible with PMMA and no entanglement between them occurs. In contrast, in h-PS solution, due to the overlap and entanglement between the PS corona and h-PS matrix, the micelles exhibit diffusion with characteristic of Γ ∝ q^α, where α = 2-2.6. For the same matrix polymer concentration, the micelles exhibit a faster diffusion in PMMA solution than that in h-PS solution, especially in semidilute solutions. The fact further indicates that the overlap and entanglement between the corona and h-PS matrix restrict the micelle motion.     

Chain conformation of polystyrene in bulk by small-angle X-ray scattering

Small-angle x-ray scattering from solid solutions of different molecular weight fractions of partially brominated polystyrene in polystyrene has been studied. The results of this study indicate that polymer chains in bulk have a radius of gyration proportional to the square root of molecular weight, which is consistent with the random coil model. However, these radii are approximately 20% larger than the unperturbed radii deduced by light scattering in dilute solutions.     

Structure of colloidal particles in water-oil mixtures stabilized by polymeric emulsifiers: 2. Small angle neutron scattering investigation

Small-angle neutron coherent scattering techniques have been used to characterize the conformation of amphiphilic macromolecules in polymeric microemulsions. The radius of gyration, the molecular weight and the aggregation number of the macromolecules within the micelles have been measured using a dilution procedure in conjunction with an adjustment of the contrast factor between polymer and solvents. Additional information on the internal structure of the micelles has been obtained from the asymptotic behaviour of the scattering form factor P(q). From considerations of the respective affinities between the two copolymer sequences and the solvent mixture, plausible models are proposed for the micellar structure.     

Association and physical gelation of ABA triblock copolymer in selective solvent

Association behavior and physical gelation mechanism of ABA triblock copolymer dissolved in B-selective solvent have been studied systematically from dilute to moderately concentrated solutions. Static and dynamic light scattering and nuclear magnetic resonance measurements for dilute solutions of poly(methyl methacrylate)-block-poly(tert-butyl acrylate)-block-poly(methyl methacrylate) (PMMA-PtBuA-PMMA) in 1-butanol (PtBuA selective solvent) indicated that PMMA-PtBuA-PMMA chains are molecularly dissolved above 50 °C. With decreasing temperature, the triblock copolymers form associated micelles consisting PMMA associated core and PtBuA shell. Linear dynamic viscoelastic measurements for solutions with moderate concentration (3.9-12.0 wt%) revealed that the system was viscous sol state at 60 °C. Drastic increase of shear storage modulus (G′) occurred with decreasing temperature, and at 25 °C, G′ showed rubbery plateau with weak frequency dependency, means the formation of elastic physical gel. The consistency between the temperature for micelle formation and that at the increase in G′ indicates that the physical gelation is owing to the network formation as the result of the association of PMMA chains and the bridging PtBuA chains connecting the PMMA cores. Master curves for the dynamic moduli were derived by time-temperature superposition along the frequency axis. Just above sol-gel transition concentration (C_gel), the master curves suggest the existence of fairy amount of aggregate that is not incorporated in the macroscopic network. With the increase in polymer concentration, the master curves become to reveal Maxwell-type viscoelasticity with narrow relaxation time distribution, suggesting the formation of transient network with easily generation and destruction of crosslinks. Concentration dependency of the plateau modulus is stronger than the theoretically expected, means the macroscopic transient network grows with polymer concentration by increasing the fraction of elastically effective bridging PtBuA chain above C_gel.     

Size exclusion chromatography with multiple detectors: Solution properties of linear chains of varying flexibility in tetrahydrofuran

Narrow molecular weight distribution polyisoprenes (PI), polybutadienes (PBD), poly(isobuty1enes) (PIB), poly(methylmethacry1ates) (PMMA), polystyrenes (PS), and poly(octadecy1 methacrylates) (PODMA) have been studied by size exclusion chromatography (SEC) in tetrahydrofuran (THF) with light scattering and viscometric detectors. The molecular weight (M) dependence of the intrinsic viscosity, [η], and radius of gyration, R_g, is reported for THF solutions of these polymers, in many instances for the first time. The availability of these data for a series of chains of varying flexibility allows a test of the universal calibration principle in SEC. Furthermore, an apparent dependence of the hydrodynamic parameter in good solvents, Φ, on chain stiffness is observed. All chains appear to exhibit hydrodynamic draining in THF. © 1996 John Wiley & Sons, Inc.     

Chain dimensions of crystallizable polymers in the solid and melt states

Small angle neutron scattering (SANS) data were obtained on hydrogenated polybutadiene, a crystallizable polymer (α_c≈0.4), which is equivalent in chemical microstructure to polyethylene with ca. 18 ethyl groups per 1000 main chain carbon atoms. One linear sample (M=62 400) and one 3-arm star (M=104 400) were used; labelled species were prepared by deuteration of the parent polybutadienes. Scattering curves were obtained in both the solid state and the melt with mixtures containing up to 30% of the labelled species. The results indicated random mixing in the melt and the rapidly crystallized solid, and only a very slight amount of segregation in the slowly crystallized solid. The scattering curves conformed to predictions for random coil molecules over a wide range of scattering vectors. The radius of gyration obtained was the same in the solid and melt states, and in close agreement with θ solvent values for polyethylene.     

Structural aspects of the LCST phase behavior of poly(benzyl methacrylate) in room-temperature ionic liquid

The structure and lower critical solution temperature (LCST) phase behavior of well-defined poly(benzyl methacrylate) (PBnMA) solution using 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide, [C₂mim][NTf₂] ionic liquid (IL) as a solvent have been studied by dynamic light scattering (DLS) and small-angle neutron scattering (SANS) at various temperatures. The SANS profiles observed for fully deuterated IL ([C₂mim]-d₁₁[NTf₂]) containing PBnMA were kept practically unchanged in the temperature range between 298 and 363 K, while they suddenly changed at 363 K. This indicates that the LCST behavior of PBnMA-IL solution is a first-order phase transition, which is consistent with the DLS results. The SANS profiles below 363 K were well represented by the theoretical Debye scattering function with inter-molecular interaction and the radius of gyration, R_g was estimated to be almost constant, i.e., ∼45 Å. The SANS result obtained here was compared with those in aqueous PNIPAm solutions as a typical LCST system, and some differences between IL and aqueous solution systems are pointed out. It is found that thermodynamic quantities (ΔH_demix, ΔS_demix and ΔG_demix) from the homogeneous solution to the phase separation states strongly depend on the solvation of the PBnMA polymer by the IL ([C₂mim] cation and [NTf₂] anion). We propose an LCST phase separation mechanism in the polymer-IL solution.     

Behaviour of poly(β-hydroxybutyric acid) in dilute solution

The refractive indices of poly(β-hydroxybutyric acid) (PHB) at four wavelengths have been determined via different procedures. Viscometric and light scattering measurements have been made on solutions of eight samples of PHB (M_w = 20·9 × 10³?929 × 10³ g mol^?1) in 2,2,2-trifluoroethanol. From the dependences of intrinsic viscosity and of radius of gyration on molar mass, the conformation of PHB in dilute solution is shown to be that of a random coil. The findings are discussed in relation to existing conflicting evidence on the conformation of this polymer.     

Phase separation in randomly charged polystyrene sulphonate ionomer solutions

The dynamics of randomly charged polystyrene caesium-sulfonate ionomers in semi-dilute solutions were studied using a combination of dynamic light scattering (DLS), small angle neutron scattering (SANS), and bulk rheology. The samples were studied in toluene solutions where the aggregation of the dipolar groups is favoured. Evidence of aggregation in dilute solution is found using DLS and SANS with both the hydrodynamic and static radius of gyration indicating that there is a contraction of the chains due to intra-chain attractive forces. SANS experiments demonstrate the evolution of the aggregates into a network structure as a function of polymer concentration. The association process is caused by the dipolar attraction between the charged groups and introduces two static correlation lengths in the mesh structure of the network; the standard semi-dilute mesh size (ξ=1.12c^{−0.72±0.03}) and an inhomogeneity length (Ξ=24c^0.58±0.05) due to micro-phase separation. The scaling of the amplitudes of the correlation lengths I₁(0)∼c^{−0.33±0.07} and I₂(0)∼c^2.0±0.4 are consistent with good solvent conditions and micro-phase separation, respectively. An imposed shear causes the break up of the micro-phase separated micellar system with a characteristic yield stress for the Bingham step-like shear thinning.     

Studies of cyclic and linear poly(dimethyl siloxanes): 12. Observation of diffusion behaviour by quasielastic neutron scattering

High resolution neutron scattering experiments have been used to observe the diffusive motion of low molecular weight linear and cyclic poly(dimethyl siloxane) molecules in dilute solution in deuterated benzene. Diffusion coefficients (D) and hydrodynamic radii (R_H) have been compared with values obtained by light scattering for higher molecular weight samples and with radii of gyration (R_g) obtained by small-angle neutron scattering. While the ratio $\text{D}{}_{\mathrm{<mtext>ring</mtext>}}\text{D}{}_{\mathrm{<mtext>chain</mtext>}}$ is close to the predicted value of 0.85, the ratio $\text{R}{}_{\mathrm{g}}\text{R}{}_{\mathrm{<mtext>H</mtext>}}$ falls below the theoretical value for both ring and chain molecules. The scattering curves show effects arising from both centre of mass diffusion and internal molecular motion, and the observed inverse correlation times are compared with calculated behaviour as a function of scattering vector, Q.     

Small-angle neutron scattering study on block and gradient copolymer aqueous solutions

The small-angle neutron scattering investigation was carried out on semi-dilute aqueous solutions of block and gradient copolymers comprising pEOVE and pMOVE, pEOVE₃₀₀-block-pMOVE₃₀₀ (Block) and p(EOVE-grad-MOVE)₆₀₀ (Grad). Here, pEOVE and pMOVE denote poly(2-ethoxyethyl vinyl ether) and poly(2-methoxyethyl vinyl ether), respectively, and the numbers indicate the degrees of polymerization. The monomer composition in the Grad had a gradient along the polymer chain. For 20.0 wt% solutions, a microphase-separated structure and physical gelation were observed both in Block and in Grad systems. In the case of the Grad system, a gradual microphase separation took place as a function of temperature via a micellization with a small radius of core, characterized by the “reel-in” process, i.e., a winding of polymer chains to the core of a micelle because of the gradient composition. On the other hand, the Block system underwent a stepwise transition with respect to temperature. The relationship between microphase separation and the rheological behavior is explained from the viewpoint of microscopic structure.     

Conformation of oligo(ethylene glycol) grafted polystyrene in dilute aqueous solutions

Temperature induced conformational changes of poly(p-oligo(ethylene glycol) styrene) (POEGS) in aqueous solutions were investigated by small angle neutron scattering (SANS), neutron transmission and dynamic light scattering (DLS). The molecular weight of the polymer studied was 9400 g/mol with a polydispersity index of 1.18 and each repeat unit of the polymer had four ethylene glycol monomer segments. The polymer was water soluble due to the hydrophilicity of the OEG side chains and these solutions showed lower critical solution temperature (LCST) depending on the concentration of the polymer. Measurements of solution behavior were made as a function of temperature in the range of 25-55 °C for three polymer concentrations (0.1 wt%, 0.3 wt%, and 1.8 wt%). Neutron transmission measurements were used to monitor the amount of polymer which precipitated or remained in solution above the cloud point temperature (T_CP). DLS revealed the presence of large clusters in all solutions both below and above T_CP while SANS provided information on the structure and interactions between individual chains. It was found that in the homogeneous region below T_CP the shape of individual polymers in solution was close to ellipsoidal with the dimensions R_a = 37 Å and R_b = 14 Å and was virtually independent of temperature. The SANS data taken for the most concentrated solution studied (1.8 wt%) were fit to the ellipsoidal model with attractive interactions which were approximated by the Ornstein-Zernike function with a temperature-dependent correlation length in the range of 24-49 Å. The collapse of individual polymers to spherical globules with the radius of 15 Å above T_CP was observed.     

Chain stiffness and chain conformation of poly(α-methylene-γ-butyrolactone) in dilute solutions

The chain stiffness and local chain conformation of atactic poly(α-methylene-γ-butyrolactone) (PMBL), which is a side chain cyclic structural analog of poly(methyl methacrylate) (PMMA), with a weight-average molecular weight (M_w) ranging from 2.8 × 10³ to 2.6 × 10⁶ in N,N-dimethylformamide (DMF) and γ-butyrolactone (GBL) were characterized by size exclusion chromatography with a multi-angle light-scattering detector (SEC-MALS) and synchrotron radiation small-angle X-ray scattering (SAXS). Based on the Kratky-Porod worm-like chain model, the scattering functions and the M_w dependence of z-average root-mean-square radius of gyration <S²>_z^1/2 yielded the Kuhn segment lengths λ⁻¹, the diameter of the PMBL chains d, and the excluded-volume strengths in DMF and GBL. The local conformation of atactic PMBL in DMF and GBL were slightly larger than those of atactic PMMA, due to the presence of the conformationally rigid lactone ring structure.     

Network properties: 3. A pulsed n.m.r. study of molecular motions in some AB-crosslinked polymers

This paper presents the results of a pulsed n.m.r. study of molecular motions in poly (methyl methacrylate) (PMMA) and poly (methyl acrylate) (PMA) chains in a series of multicomponent network polymers consisting of poly (vinyl trichloroacetate) (PVTCA) crosslinked with PMMA and with PMA, with emphasis on segmental motions. Results of ancilliary broad line n.m.r. and dilatometric studies are included; the latter demonstrate that in PMA containing polymers microphase separation of the components is complete while in PMMA containing polymers a mixed microphase of PVTCA and PMMA and a pure PMMA microphase are formed. α-Methyl group rotations in PMMA chains and segmental motions in both PMMA and PMA chains are modified with respect to those in the corresponding homopolymers. Modifications to the segmental motions in the crosslinking chains are attributed to the fact that their chain ends are attached to PVTCA chains. It is considered that the comparative rigidity of PVTCA chains (T_g ～ 60°C) reduces segmental motions in at least portions of the PMA chains (T_g ～ 5°C) while the comparative mobility of PVTCA enhances segmental motions in PMMA (T_g ～ 100°C). Thus the molecular mobility of chains of one polymer is to some extent transmitted to chains of another polymer to which it is attached.     

Supramolecular structures of an amphiphilic hairy-rod conjugated copolymer bearing poly(ethylene oxide) side chain

The structures of an amphiphilic conjugated graft copolymer, poly(2,3-diphenyl-5-(trimethylene-heptadeca(oxyethylene)-methoxy-phenylene vinylene) (denoted as PVEO₁₇) composing of a conjugated DP-PPV backbone and PEO side chains, in bulk and solutions with tetrahydrofuran (THF) and water have been investigated by small-angle X-ray scattering (SAXS). In bulk state, the DP-PPV main chains in PVEO₁₇ stacked to form flat disk microdomains dispersed in the PEO side-chain matrix. The corresponding wide angle X-ray scattering pattern revealed the existence of crystallinity of the PEO side chains. The structure of the polymer in solution was affected by the solvent quality and the polymer concentration. PVEO₁₇ chains were relatively well dispersed in THF. In aqueous solutions, however, the amphiphilic PVEO₁₇ chains aggregated significantly over the concentration range of 1–8 wt%, where the polymer was found to self-organize to form cylindrical micelles with the aggregation number increasing with the increase of concentration. The photophysical properties characterized by UV–Vis and photoluminescence spectroscopy were strongly affected by the aggregation state of the polymer.     

Solution properties of polyaniline

Solution properties of polyaniline (PANI) synthesized at various temperatures were studied using static light scattering (SLS), intrinsic viscosity, and dynamic light scattering (DLS). We demonstrated that average radius of gyration 〈R_g〉, intrinsic viscosity [η], and average hydrodynamic radius 〈R_H〉, of polyaniline molecules in dilute N‐methyl‐2‐pyrrolidinone (NMP) solutions increased with decreasing synthesis temperatures, i.e.; increasing molecular weight. SLS data demonstrate that second virial coefficient (A₂) decreased with increasing particle sizes suggesting that solubility of PANI in NMP decreased with increasing particle sizes. We also find that the polymers extend as the polymer concentration is lowered and that the increase in the hydrodynamic radius can be expressed by a power law of the electrostatic screening length. This behavior is typical of polyelectrolytes in dilute solution, providing a basis for understanding the conformation changes of this metallic polymer in solution. Copyright © 2009 Society of Chemical Industry     

Dynamics of ESIPT fluorescent methylmethacrylate-benzazole dye copolymers

The dynamics of fluorescent methylmethacrylate-benzazole dye copolymers were investigated in different concentration regimes by dynamic light scattering. In the dilute regime the polymer behaves as typical polydisperse linear chains in good solvent with a dynamics dominated by a single fast mode. In the semidilute regime, the cooperative diffusion coefficient, D_coop and the correlation length, ξ could be obtained. Above the semidilute regime the intensity autocorrelation functions show two-step decays, indicating the existence of low range correlations. The dye incorporation, even though small, affects the copolymer dynamics behavior in concentrated solutions if compared to PMMA, which is probably ascribed to a polymer-solvent interaction.