Solution properties of NR/PU block copolymers by size‐exclusion chromatography and viscometry

Soluble block copolymers based on natural rubber and polyurethane oligomers derived from 1,3 butane diol and toluene diisocyanate were synthesized for the first time. The dilute solution properties of these block copolymers dissolved in tetrahydrofuran (THF) were studied by viscometry and gel permeation chromatography (GPC). The Mark–Houwink constants K and a of the block copolymer system were determined by the molecular weight data from GPC combined with the viscosity data. Both the values were found to be in the range usually given by flexible elastomers. The intrinsic viscosity values were found to decrease successively with a decrease in the NCO/OH ratio from 1.12 to 1.05. The unperturbed chain parameters, K_θ and B were determined from the viscosity data. The K_θ calculated was used to get the unperturbed end‐to‐end distance and radius of gyration of the block copolymer systems in THF. The viscosity data were also used to study the chain conformation in dilute solutions. It was found that the molecules adopt a compressed core and shell conformation in which the higher molecular weight component, NR, forms the shell, which compresses the PU core. All the block copolymers assume a compressed segregated core and shell model which changes to a partially segregated core and shell conformation, or partially Gaussian conformation, at the transition temperature located at 70 °C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2104–2111, 2006     

Viscometric properties of dilute polystyrene/dioctyl phthalate solutions

We report viscometric data collected in a Couette rheometry on dilute, single‐solvent polystyrene (PS)/dioctyl phthalate (DOP) solutions over a variety of polymer molecular weights (5.5 × 10⁵ ≤ M_w ≤ 3.0 × 10⁶ Da) and system temperatures (288 K ≤ T ≤ 318 K). In view of the essential viscometric features, the current data may be classified into three categories: The first concerns all the investigated solutions at low shear rates, where the solution properties are found to agree excellently with the Zimm model predictions. The second includes all sample solutions, except for high‐molecular‐weight PS samples (M_w ≥ 2.0 × 10⁶ Da), where excellent time–temperature superposition is observed for the steady‐state polymer viscosity at constant polymer molecular weights. No similar superposition applies at a constant temperature but varied polymer molecular weights, however. The third appears to be characteristic of dilute high‐molecular‐weight polymer solutions, for which the effects of temperature on the viscosity curve are further complicated at high shear rates. The implications concerning the relative importance of hydrodynamic interactions, segmental interactions, and chain extensibility with increasing polymer molecular weight, system temperature, and shear rate are discussed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 787–794, 2006     

Effects of polymer structure on reactivity of functional groups in reduction reaction using tin hydride soluble supports

The influence of macromolecular chains onto reactivity of the grafted functional group has been investigated through reduction of 6‐bromohexene using tin hydride soluble polymer supports. Kinetic investigations clearly indicate a retarding effect of the polymer structure on the substrate diffusion. Correlations of molecular weight and degree of functionalization with reactivity of the functional lateral groups are discussed. In dilute regime, an increasing of internal density of the polymer coil leads to a diminution of the rate constant k_H. Thus, the higher density of the coil limits the substrates diffusion, which favors the radical cyclization and so formation of the cyclic product. At the opposite, in concentrated regime formation of the acyclic product, hex‐1‐ene is favored despite the higher viscosity of such medium that should limit the diffusion. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5954–5964, 2006     

Unified analysis of thermodynamic and rheological properties of high polymer solutions. I. Binary systems

We present a comprehensive experimental study of thermodynamic and rheological properties of semidilute polymer solutions in good solvent. Osmotic pressure and viscosity measurements have been done in several polymer‐solvent systems at different temperatures. A renormalization group technique was applied to analyze the data using de Gennes's blobs model to connect dynamic and conformational quantities. The behavior of polymer systems in the whole range from dilute to semidilute solutions can be satisfactorily described using only a few nonuniversal quantities experimentally determined. An adequate agreement between experiments and theory was found, showing universal behavior with a system‐dependent constant β that does not depend on molecular weight or concentration. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 290–301, 2002     

Stimuli‐responsive ampholytic terpolymers of N‐acryloyl‐valine,acrylamide, and (3‐acrylamidopropyl)trimethylammonium chloride: Synthesis,characterization, and solution properties

Low‐charge density ampholytic terpolymers composed of acrylamide (AM), (3‐acrylamidopropyl)trimethyl ammonium chloride (APTAC), and N‐acryloyl‐valine were prepared via free‐radical polymerization in 0.5 M NaCl to yield terpolymers with random charge distributions. Sodium formate (NaOOCH) was employed as a chain transfer agent during the polymerization to suppress gel effects and broadening of the molecular weight distribution (MWD). Terpolymer compositions were determined by ¹³C NMR spectroscopy. Terpolymer molecular weights (MWs) and polydispersity indices (PDIs) were obtained via size exclusion chromatography/multi‐angle laser light scattering (SEC‐MALLS). Intrinsic viscosity values determined from SEC‐MALLS data using the Flory–Fox relationship were compared with those determined by low‐shear dilute solution viscometry and found to be in good agreement. SEC‐MALLS experiments allowed examination of radius of gyration‐MW (R_g‐M) relationships and the Mark‐Houwink‐Sakurada intrinsic viscosity‐MW ([η]‐M) relationships for terpolymers. The R_g‐M and [η]‐M relationships indicated little or no excluded volume effects under SEC conditions indicating that the terpolymers were in near theta conditions in an aqueous buffer solution. Potentiometric titration experiments were performed in deionized (DI) water. These studies revealed that the apparent pK_a of the AMVALTAC terpolymers increases with increasing VAL content. The solution properties of low‐charge density ampholytic terpolymers have been studied as functions of solution pH, ionic strength, and polymer concentration. The charge‐balanced terpolymers exhibit polyampholyte behavior at pH values ≥ 6.5. As solution pH is decreased, these charge‐balanced terpolymers become increasingly cationic due to the protonation of the VAL repeat units. Charge‐imbalanced terpolymers generally exhibit polyelectrolyte behavior, although the effects of intramolecular electrostatic interactions (e.g., polyampholyte effects) on the hydrodynamic volume are evident at certain values of solution pH and salt concentration. The solution behavior of the terpolymers in the dilute regime correlates well with that predicted by various polyampholyte solution theories. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3125–3139, 2006     

Synthesis and properties of a new fluorine‐containing polybenzimidazole for high‐temperature fuel‐cell applications

An amorphous, organosoluble, fluorine‐containing polybenzimidazole (PBI) was synthesized from 3,3′‐diaminobenzidine and 2,2‐bis(4‐carboxyphenyl)hexafluoropropane. The polymer was soluble in N‐methylpyrrolidinone and dimethylacetamide and had an inherent viscosity of 2.5 dL/g measured in dimethylacetamide at a concentration of 0.5 g/dL. The 5% weight loss temperature of the polymer was 520 °C. Proton‐conducting PBI membranes were prepared via solution casting and doped with different amounts of phosphoric acid. In the methanol permeability measurement, the PBI membranes showed much better methanol barrier ability than a Nafion membrane. The proton conductivity of the acid‐doped PBI membranes increased with increasing temperatures and concentrations of phosphoric acid in the polymer. The PBI membranes showed higher proton conductivity than a Nafion 117 membrane at high temperatures. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4508–4513, 2006     

Rheology of concentrated blends with immiscible components

The rheology and morphology evolution of nondilute and concentrated immiscible blends were investigated in this paper. A theoretical model was established by a Hamiltonian formalism. The interactions between droplets were integrated in the morphology‐dependent drag coefficient. The phenomenological parameters in the model were determined by the comparisons with the dilute emulsion model and the Krieger–Dougherty model. The model showed better predictions in the shear viscosity and first normal stress difference than that of the dilute emulsion model. The effects of volume fraction on droplet deformation were also predicted and compared with the numerical simulations. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2534–2540, 2005     

Photoactive,liquid‐crystalline,hyperbranched benzylidene polyesters: Synthesis and characterization

A novel photoactive, liquid‐crystalline, hyperbranched benzylidene polyester (PAHBP) was synthesized from a dilute solution of an A₂ photoactive monomer [bis(4‐hydroxybenzylidene)‐4‐phenyl cyclohexanone] and a B₃ monomer (1,3,5‐benzene tricarboxylic acid chloride) by the solution polycondensation method in the presence of pyridine as a condensing agent. PAHBP was thoroughly characterized by Fourier transform infrared, ¹H and ¹³C NMR, ultraviolet–visible spectrometry, and gel permeation chromatography. The inherent viscosity of the polymer was 0.35 dL/g in tetrahydrofuran. The degree of branching was 0.53, which confirmed the branched architecture of the polymer. Furthermore, thermogravimetric analysis, differential scanning calorimetry, and polarized optical microscopy were used to examine the thermal stability and thermotropic liquid‐crystalline properties of the hyperbranched polyester. The polymer exhibited a nematic mesophase over a wide range of temperatures. The photoreactivity of PAHBP was studied by photolysis under ultraviolet light. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 53–61, 2006     

Viscometric investigation of intramolecular hydrogen bonding cohesional entanglement in extremely dilute aqueous solution of poly vinyl alcohol

An investigation of influence of cryogenic treatment on extremely dilute aqueous solution of poly(vinyl alcohol) (PVA) was performed by viscometry. The solution was frozen in liquid nitrogen or in a freezer at −25°C, then thawed at ambient temperature and concentrated by evacuation. The viscosity of the solution was measured using the dilute method. The experimental results indicated that the viscosity of the solution is related to N, the times of the freezing and thawing cycle, and the temperature for freezing. Undergoing a treatment of freezing and thawing, the viscosity of the solution is decreased, while it can be recovered the value of before the treatment as the solution had been heated at a high temperature. Thus, a conclusion may be obtained; that is, for an extremely dilute aqueous solution of PVA, which concentration is below C_gel, threshold concentration for gelation, an intramolecular hydrogen bonding cohesional entanglement can be formed by freezing as N < 5. However, in the case of N > 5, it not only formed an intramolecular hydrogen bonding but also produced an intermolecular hydrogen bonding. At the same time, the abnormal behavior of reduced viscosity of the solution in extremely dilute concentration region has been explained. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 2421–2427, 1997     

A predictive approach based on the Simha–Somcynsky free‐volume theory for the effect of dissolved gas on viscosity and glass transition temperature of polymeric mixtures

The gas concentration and pressure effects on the shear viscosity of molten polymers were modeled by using a unified approach based on a free volume theory. A concentration and pressure dependent “shift factor,” which accounts for free volume changes associated with polymer‐gas mixing and with variation of absolute pressure as well as for dilution effects, has been herein used to scale the pure polymer viscosity, as evaluated at the same temperature and atmospheric pressure. The expression of the free volume of the polymer/gas mixture was obtained by using the Simha and Somcynsky equation of state for multicomponent fluids. Experimental shear viscosity data, obtained for poly(ε‐caprolactone) with nitrogen and carbon dioxide were successfully predicted by using this approach. Good agreement with predictions was also found in the case of viscosity data reported in the literature for polystyrene and poly(dimethylsiloxane) with carbon dioxide. Free volume arguments have also been used to predict the T_g depression for polystyrene/carbon dioxide and for poly(methyl methacrylate)/carbon dioxide mixtures, based on calculations performed, again, with the Simha and Somcynsky theory. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1863–1873, 2006     

Charge density effects in salt‐free polyelectrolyte solution rheology

Solution rheology of 2‐vinyl pyridine and N‐methyl‐2‐vinyl pyridinium chloride random copolymers in ethylene glycol was studied over wide ranges of concentration and effective charge. The fraction of quaternized monomers α and the fraction of monomers bearing an effective charge f of these copolymers were measured using counterion titration and dielectric spectroscopy, respectively. Ethylene glycol is a good solvent for neutral poly(2‐vinyl pyridine), with very few ionic impurities. The viscosity η and relaxation time τ of dilute and semidilute unentangled solutions exhibit the scaling with concentration and effective charge expected by the Dobrynin model. Reduced viscosity data are independent of concentration in dilute solution, giving an intrinsic viscosity that depends on effective charge, and the experimental data obey the Fuoss law in the semidilute unentangled regime. Scaling concentration with the overlap concentration (c/c*) reduces these data to common curves, and c* ～ f ^?12/7 as predicted by the Dobrynin model, where f is the fraction of monomers bearing an effective charge. While the overlap concentration depends strongly on effective charge until counterion condensation occurs, the entanglement concentration c_e is surprisingly insensitive to effective charge, indicating that entanglement effects are not understood using the Dobrynin model. The terminal modulus G = η/τ depends only on the number density of chains G = ckT/N for c* < c < c_e, and G ～ c^3/2 for c > c_e independent of the effective charge. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2001–2013, 2006     

Star polystyrenes by anionic star–star coupling reactions with divinylbenzene

The incremental addition of divinylbenzene was used to generate star polystyrenes in a nearly full conversion of a living polystyrenyl anion. The dramatic increase in the molecular weight of the star polystyrenes with a limited supply of the living polystyrene supported the formation of gradient‐star polystyrenes through star–star coupling. The stoichiometric analysis of the star polymers revealed that their connection polymer had a shorter length than their branch polymer. The measured solution viscosity of the gradient‐star polymers greatly deviated from a linear correlation with the molecular weight and was in parallel to a theoretical simulation based on a highly branched structure of the gradient‐star polymer. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2579–2586, 2006     

Viscosity effects in cobaloxime‐mediated catalytic chain‐transfer polymerization of methacrylates

The effect of bulk viscosity on the cobaloxime‐mediated catalytic chain‐transfer polymerization of methacrylates at 60 °C was investigated by both the addition of high molecular weight poly(methyl methacrylate) to methyl methacrylate polymerization and the dilution of benzyl methacrylate polymerization by toluene. The results indicate that the bulk viscosity is not directly linked to the chain‐transfer activity. The previously measured relationship between chain‐transfer‐rate coefficient and monomer viscosity therefore probably reflects changes at the molecular level. However, the results in this article do not necessarily disprove a diffusion‐controlled reaction rate because cobaloxime diffusion is expected to scale with the monomer friction coefficient rather than bulk viscosity. Considering the published data, to date we are not able to distinguish between a diffusion‐controlled reaction rate or a mechanism directly affected by the methacrylate substituent. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 782–792, 2002; DOI 10.1002/pola.10152     

Synthesis and characterization of new carbazole/fluorene‐based derivatives for blue‐light‐emitting devices

2,7‐Bis(9‐ethylcarbazol‐3‐yl)‐9,9‐di(2‐ethylhexyl)fluorene and a segmented copolymer composed of the same chromophores alternated with hexamethylene fragments were synthesized. The obtained materials possess good solubility in common organic solvents, high thermal stability with 1% weight loss temperature of 350–370 °C, and suitable glass transition temperatures. Both derivatives show blue fluorescence in dilute solutions as well as in solid state, demonstrating that excimers are not formed in the thin films. The fluorescence spectra of the materials do not show any peaks in the long‐wavelength region even after annealing at 200 °C in air. An organic LED with the configuration of ITO/copolymer/Al generates blue electroluminescence with the maximum peak at 416 nm, rather low turn‐on voltage (4.0 V), and brightness of about 400 cd/m². The heterostructure device based on model derivative emitted stable blue light with low operation voltage (100 cd/m² at ～11 V) and demonstrated luminescence efficiency of 0.8 cd/A. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5987–5994, 2006     

Dilute solution properties of cellulose in LiOH/urea aqueous system

Cellulose was dissolved rapidly in 4.6 wt % LiOH/15 wt % urea aqueous solution and precooled to –10 °C to create a colorless transparent solution. ¹³C‐NMR spectrum proved that it is a direct solvent for cellulose rather than a derivative aqueous solution system. The result from transmission electron microscope showed a good dispersion of the cellulose molecules in the dilute solution at molecular level. Weight‐average molecular weight (M_w), root mean square radius of gyration (〈s²〉_z^1/2), and intrinsic viscosity ([η]) of cellulose in LiOH/urea aqueous solution were examined with laser light scattering and viscometry. The Mark–Houwink equation for cellulose in 4.6 wt % LiOH/15 wt % urea aqueous solution was established to be [η] = 3.72 × 10^?2 M in the M_w region from 2.7 × 10⁴ to 4.12 × 10⁵. The persistence length (q), molar mass per unit contour length (M_L), and characteristic ratio (C_∞) of cellulose in the dilute solution were given as 6.1 nm, 358 nm^?1, and 20.8, respectively. The experimental data of the molecular parameters of cellulose agreed with the Yamakawa–Fujii theory of the worm‐like chain, indicating that the LiOH/urea aqueous solution was a desirable solvent system of cellulose. The results revealed that the cellulose exists as semistiff‐chains in the LiOH/urea aqueous solution. The cellulose solution was stable during measurement and storage stage. This work provided a new colorless, easy‐to‐prepare, and nontoxic solvent system that can be used with facilities to investigate the chain conformation and molecular weight of cellulose. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3093–3101, 2006     

Investigating the Dynamic Viscoelasticity of Single Polymer Chains using Atomic Force Microscopy

In single‐molecule force spectroscopy (SMFS), many studies have focused on the elasticity and conformation of polymer chains, but little attention has been devoted to the dynamic properties of single polymer chains. In this study, we measured the energy dissipation and elastic properties of single polystyrene (PS) chains in toluene, methanol, and N,N‐dimethylformamide using a homemade piezo‐control and data acquisition system externally coupled to a commercial atomic force microscope (AFM), which provided more accurate information regarding the dynamic properties of the PS chains. We quantitatively measured the chain length‐dependent changes in the stiffness and viscosity of a single chain using a phenomenological model consistent with the theory of viscoelasticity for polymer chains in dilute solution. The effective viscosity of a polymer chain can be determined using the Kirkwood model, which is independent of the intrinsic viscosity of the solvent and dependent on the interaction between the polymer and solvent. The results indicated that the viscosity of a single PS chain is dominated by the interaction between the polymer and solvent. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1736–1743     

Synthesis and comparative solution properties of single‐, twin‐, and triple‐tailed associating ionic polymers based on diallylammonium salts

The cycloterpolymerizations of single‐, twin‐, and triple‐tailed hydrophobes with hydrophilic monomer N,N‐diallyl‐N‐carboethoxymethylammonium chloride and sulfur dioxide afforded a series of cationic polyelectrolytes (CPEs) in excellent yields. These CPEs, upon the acidic hydrolysis of the pendent ester groups, gave the corresponding pH‐responsive cationic acid salts, which, upon a treatment with sodium hydroxide, were converted to polybetaines (PBs), anionic polyelectrolytes (APEs), and PB/APE polymers containing various proportions of zwitterionic (PB) and anionic fractions (APE) in the polymer chain. At a shear rate of 0.36 s⁻¹ at 30 °C, salt‐free water solutions of the CPEs (2 g/dL) containing 8, 4, and 2.67 mol % of the single‐, twin‐, and triple‐tailed hydrophobes (all having 8 mol % octyloxy tails) had apparent viscosity values of 70, 2800, and 396,000 cps, respectively. The PB/APE polymer with a ratio of 33:67 for the zwitterionic and anionic fractions in the polymer chain gave the highest viscosity value. The superior viscosity behavior of the polymers containing the triple‐tailed hydrophobe was attributed to the blocky nature of the comonomer. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5480–5494, 2006     

Fibrillar structure of self‐assemblies formed from heterocomplementary monomers linked through sextuple hydrogen‐bonding arrays

The nanostructure of the fibrillar supramolecular aggregates generated in decane solutions of homoditopic heterocomplementary monomers forming sextuple hydrogen‐bond‐mediated self‐assemblies was investigated by small‐angle neutron scattering and cryogenic‐temperature transmission electron microscopy. The persistence length (L_p) of the fibrillar aggregates was found to be ～18 nm, as inferred from combined measurements of the radius of gyration and of the contour length. The values of both the weight‐average molecular weight and the mass per unit length of the fibers suggest that the latter consist of few aggregated monomolecular wires. At T = 25 °C, the formation of branched aggregates occurs around the crossover concentration, C*, between the dilute and semidilute regimes, whereas the classical behavior of equilibrium polymers is observed at T = 65 °C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 103–115, 2007     

Dynamics of poly(p‐phenylene) ladder polymers in solution

Photon correlation spectroscopy in both polarized and depolarized geometry was employed to investigate the dynamics of a ribbon‐type polymer exhibiting good solubility. In dilute solution, the translational diffusion for all examined molecular weights has confirmed the picture of wormlike chains with rather short (∼ 7 nm) persistence length (Macromolecules 1997, 30, 273). In the semidilute regime, the total concentration fluctuations display, besides the fast dominant cooperative diffusion, a second slower diffusive process that exhibits weak concentration dependence and is not related to the self‐diffusion measured by pulse‐field‐gradient NMR. The concentration dependence of the cooperative and the self‐diffusion coefficient as well as of the zero‐shear viscosity cannot be consistently described by neither flexible nor stiff chain models. Presence of aggregates was revealed at high concentrations. Owing to the short persistence length, the rotational diffusion is too fast to be adequately investigated. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2211–2220, 1999     

Studies of the solution properties of sulfonated-(styrene-(ethyrene-CO-butylene)-styrene) block copolymer

The dilute solution properties of lightly sulfonated hydrogenated styrene-butadiene-styrene block copolymer (S-SEBS) dissolved in tetrahydrofunan (THF) were studied by viscometry. The ring conformation in dilute regime can be deduced from the intrinsic viscosity data. It is believed that this special conformation results from the location of ionic group at both two-end blocks. The intermolecular aggregation can be observed when the solutions undergo the freezing–thawing process in the same concentration region. The extent of aggregation is affected by the freezing–thawing cycle times, water content in THF, and the counterion radii, etc. The properties of the aggregation equilibrium are also discussed. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2677–2681, 1998