Polymers In Polar Solvents Research Articles

Phase Behavior of Ion-Containing Polymers in Polar Solvents: Predictions from a Liquid-State Theory with Local Short-Range Interactions

The thermodynamic phase behavior of charged polymers is a crucial property underlying their role in biology and various industrial applications. A complete understanding of the phase behaviors of such polymer solutions remains challenging due to the multi-component nature of the system and the delicate interplay among various factors, including the translational entropy of each component, excluded volume interactions, chain connectivity, electrostatic interactions, and other specific interactions. In this work, the phase behavior of partially charged ion-containing polymers in polar solvents is studied by further developing a liquid-state (LS) theory with local shortrange interactions. This work is based on the LS theory developed for fully-charged polyelectrolyte solutions. Specific interactions between charged groups of the polymer and counterions, between neutral segments of the polymer, and between charged segments of the polymer are incorporated into the LS theory by an extra Helmholtz free energy from the perturbed-chain statistical associating fluid theory (PC-SAFT). The influence of the sequence structure of the partially charged polymer is modeled by the number of connections between bonded segments. The effects of chain length, charge fraction, counterion valency, and specific short-range interactions are explored. A computational App for salt-free polymer solutions is developed and presented, which allows easy computation of the binodal curve and critical point by specifying values for the relevant model parameters.

Electrostatics, conformation, and rheology of unentangled semidilute polyelectrolyte solutions

Polyelectrolyte (PE) solutions, which are charged polymers in polar solvents, are ubiquitous and essential to life. Due to the electrostatic interactions among the charged monomers and mobile ions, the dependence of the rheological properties on the polymer concentration of PE solutions differs significantly from that of solutions of uncharged macromolecules. In addition, salt in PE solutions, whether added intentionally or intrinsically present, can affect the properties of the solutions. Here, we analyze the ion distribution near a monomer using the nonlinear Poisson–Boltzmann equation for scenarios with nonoverlapping and overlapping electric double layers. Consequently, by incorporating the electrostatic interactions into the blob model and Zimm–Rouse dynamic model, we obtain different scaling laws for the electrostatic energy per monomer, correlation length, end-to-end distance, relaxation time and viscosity η of semidilute, unentangled PE solutions in consecutive regimes of polymer concentration np, and salt concentration ns, which are summarized in tables. With our theory, we anticipate that the empirical Fuoss law η∝np1/2 is expected for solutions prepared with salt-contaminated PE samples, while η∝np0.68 might be found for those with purer PE samples. A new critical charge fraction φc is defined, where we predict that the peak, which is present in the measurements of the reduced viscosity η/np as a function of np, is only expected for weakly charged PEs φ<φc prepared with pure PE samples. Comparisons with the experimental data as well as the classical scaling theories are provided, and the range of applicability of the theory is discussed.

Influence of Salt on the Viscosity of Polyelectrolyte Solutions.

Polyelectrolytes (PEs) are charged polymers in polar solvents. Classical scaling theories suggest that the viscosity η for semidilute unentangled PE solutions in θ solvents obeys the empirical Fuoss law η∝n_{p}^{1/2} in the "salt-free" regime, and η∝n_{p}^{5/4} in the regime affected by added salt, where the polymer concentration n_{p} is defined as the number of monomers per volume. However, recent experiments have also reported η∝n_{p}^{0.68} and η∝n_{p}^{0.91}, which are at odds with the classical scaling theories. To rationalize the four distinct scaling laws, we probe the electrostatic energy per monomer under the influence of salt and their contributions to the viscosity of PE solutions. We identify four consecutive regimes dependent on the magnitude of the ratio of the polymer concentration n_{p} to the salt concentration n_{s}, which capture the unexplained observations, and provide physical insights for the influence of salt contamination and added salt on the properties of both weakly and strongly charged semidilute unentangled PE solutions.

Photoinitiated Dispersion Polymerization of Crosslinked Polymer in Polar Solvents: Effect of Reaction Parameter on Morphology, Size and Size Distribution and Yield

Crosslinked polymer beads were prepared by photoinitiated dispersion polymerization in a mixture of ethanol and water. In this study, the effect of types of photoinitiator, types of monomer and reaction times on particles morphology, size and size distribution and yield were investigated. Better quality of poly(st-co-EGDMA-co-VBC) obtained compared to poly(methylmethacrylate-co- EGDMA-co-VBC). However, the yield of poly(st-co-EGDMA-co-VBC) lower than poly(methylmethacrylate-co-EGDMA-co-VBC). On this regard, poly(methylmethacrylate-co-EGDMA-co-VBC) was selected to investigate further. Changing the types of photoinitiator managed to increase the quality and size of poly(methylmethacrylate-co-EGDMA-co-VBC) particles but yield obtained was decreasing. Meanwhile, longer reaction time leading to high yield and bigger size of poly(methylmethacrylate-co-EGDMA-co- VBC) particles but with lower quality. For all cases, FTIR analysis proved all functional groups have successfully attached to the polymeric backbone.

Vertical Phase Segregation Induced by Dipolar Interactions in Planar Polymer Brushes

We present a generalized theory for studying structural properties of a planar dipolar polymer brush immersed in a polar solvent. We show that an explicit treatment of the dipolar interactions yields a macroscopic concentration dependent effective “chi” (the Flory–Huggins-like interaction) parameter. Furthermore, it is shown that the concentration dependent chi parameter promotes phase segregation in polymer solutions and brushes so that the polymer-poor phase consists of a finite/nonzero polymer concentration. Such a destabilization of the homogeneous phase by the dipolar interactions appears as vertical phase segregation in a planar polymer brush. In a vertically phase segregated polymer brush, the polymer-rich phase near the grafting surface coexists with the polymer-poor phase at the other end. Predictions of the theory are directly compared with prior reported experimental results for dipolar polymers in polar solvents. Excellent agreements with the experimental results are found, hinting that the di...

Synthesis of Spiropyran Photochromic Polymer

Photochromic spiropyran material is of the most extensive and in-depth category. Small molecule spiropyran ring by UV irradiation, the color is less stable body, which restricts the widespread use of these compounds. In this paper, the introduction of spiropyran compounds with substituents on the group method of open-loop stability, which will contain active groups spiropyran monomers in the polymer side chain connected to a rigid polymer to limit the use of spiropyran ring merocyanine body rotation, so that the body color is more stable. This selection and design of the process is simple with R = CH2OCOC (CH3) =CH2 groups spiropyran monomer compounds, and then with methyl methacrylate polymer formed by radical means. By IR, NMR spectroscopy, mass spectrometry and gel permeation chromatography of the target compounds were characterized. UV spectrometer using the compounds of new photochromic properties were tested and the results shows spiropyran monomers and polymers have good photochromic properties. Discoloration kinetic of the spiropyran monomers and polymers in polar solvents proved to the spiropyran side connected to the polymer chain can significantly improve the stability of the color body.

Electron‐Rich Alcohol‐Soluble Neutral Conjugated Polymers as Highly Efficient Electron‐Injecting Materials for Polymer Light‐Emitting Diodes

AbstractWe report the design and synthesis of three alcohol‐soluble neutral conjugated polymers, poly[9,9‐bis(2‐(2‐(2‐diethanolaminoethoxy) ethoxy)ethyl)fluorene] (PF‐OH), poly[9,9‐bis(2‐(2‐(2‐diethanol‐aminoethoxy)ethoxy)ethyl)fluorene‐alt‐4,4′‐phenylether] (PFPE‐OH) and poly[9,9‐bis(2‐(2‐(2‐diethanolaminoethoxy) ethoxy)ethyl)fluorene‐alt‐benzothiadizole] (PFBT‐OH) with different conjugation length and electron affinity as highly efficient electron injecting and transporting materials for polymer light‐emitting diodes (PLEDs). The unique solubility of these polymers in polar solvents renders them as good candidates for multilayer solution processed PLEDs. Both the fluorescent and phosphorescent PLEDs based on these polymers as electron injecting/transporting layer (ETL) were fabricated. It is interesting to find that electron‐deficient polymer (PFBT‐OH) shows very poor electron‐injecting ability compared to polymers with electron‐rich main chain (PF‐OH and PFPE‐OH). This phenomenon is quite different from that obtained from conventional electron‐injecting materials. Moreover, when these polymers were used in the phosphorescent PLEDs, the performance of the devices is highly dependent on the processing conditions of these polymers. The devices with ETL processed from water/methanol mixed solvent showed much better device performance than the devices processed with methanol as solvent. It was found that the erosion of the phosphorescent emission layer could be greatly suppressed by using water/methanol mixed solvent for processing the polymer ETL. The electronic properties of the ETL could also be influenced by the processing conditions. This offers a new avenue to improve the performance of phosphorescent PLEDs through manipulating the processing conditions of these conjugated polymer ETLs.

A novel polyaniline–maleicacid–dodecylhydrogensulfate salt: Soluble polyaniline powder

A novel soluble polyaniline powder, polyaniline–maleicacid–dodecylhydrogensulfate salt was synthesized directly via emulsion polymerization pathway using benzoyl peroxide oxidant, sodium dodecyl sulfate surfactant and maleic acid as effective dopant. Dry polyaniline powder is soluble in polar solvents like DMF, NMP, DMSO and maximum solubility was found to be 6% w/v. In this emulsion polymerization pathway, both acid group (maleic acid – 0.21 U per aniline group) and surfactant molecule (dodecylhydrogensulfate – 0.25 U per aniline group) were incorporated as dopant in the polyaniline chain. Long and nonpolar chain dopant present in the polyaniline chain may provide space for the polyaniline backbone and allows the penetration of solvent molecules inside the chain and induces solubility of polymer in polar solvents. Polyaniline salt showed nano sphere morphology with average diameter of 200 nm size. The influence of synthetic conditions such as the duration of the reaction, concentration of the reactants and solvent medium on the properties of polyaniline was investigated to determine the optimum conditions for the synthesis of polyaniline salt. The conductivity of polyaniline salt was found to be 10 −1 S/cm.

Adaptation of the molecular imprinted polymers towards polar environment

A new simple method for the post-polymerisation treatment of molecularly imprinted polymers was proposed. A layer of mineral oil was deposited onto the surface of the polymer in order to create a hydrophobic environment in the binding sites and to improve the recognition properties of the polymer in polar solvents. The testing of polymers performed in acetonitrile showed that the modified polymers possessed significantly increased selectivity as compared with non-treated ones. The three-fold improvement of recognition of the template (cocaine) was achieved; the same time, for non-specific molecule (morphine) the improvement was only 1.3 times. The investigation of the stability of mineral oil coating on the polymer surface suggested that the effect produced is stable over a long period of time. This approach could be used to broaden the range of experimental conditions where molecularly imprinted polymers can perform successfully.

Polymerization and complex formation of phthalocyanine substituted by trioxyethylene in solution

Phthalocyanine substituted by eight trioxyethylenemonomethylethers (EOPc) was prepared, and the solvent effect on the polymerization has been studied at 25.0 °C through absorption and emission spectroscopies. EOPc is soluble in a wide range of solvents from water to nonpolar solvents because of the amphiphilic property of the compound. EOPc predominantly is present as a polymer in polar solvents, such as water. The degree of dissociation to monomer in nonpolar solvent increases by the increase in the E T value (acceptor) of the solvent, and it completely dissociates to monomer in chloroform. The complex formation with alkali metal ions in chloroform was studied by means of H-1 NMR spectroscopy. The structure of the complex, in which the metal ion is pinched by two trioxyethylene groups locating close to the benzene group, was estimated. The degree of polymerization increases by the complex formation in relatively low E T solvents, such as carbon tetrachloride, although the complex is hardly polymerized in chloroform. The structure of the ion pair of the complex with picrate ion was estimated.

Hyperbranched aromatic poly(ether imide)s: Synthesis, characterization, and modification

The synthesis and characterization of hyperbranched aromatic poly(ether imide)s are described. An AB2 monomer, which contained a pair of phenolic groups and an aryl fluoro moiety activated toward displacement by the attached imide heterocyclic ring, was prepared. The nucleophilic substitution of the fluoride with the phenolate groups led to the formation of an ether linkage and, subsequently, to the hyperbranched poly(ether imide), which contained terminal phenolic groups. A similar one-step polymerization involving a monomer that contained silyl-protected phenols yielded a hyperbranched poly(ether imide) with terminal silylated phenols. The degree of branching of these hyperbranched polymers was approximately 55%, as determined by a combination of model compound studies and 1H NMR integration experiments. End-capping reactions of the terminal phenolic groups were readily accomplished with a variety of acid chlorides and acid anhydrides. The nature of the chain-end groups significantly influenced physical properties, such as the glass-transition temperature and the solubility of the hyperbranched poly(ether imide)s. As the length of the acyl chain of the terminal ester groups increased, the glass-transition temperature value for the polymer decreased, and the solubility of the polymer in polar solvents was reduced, becoming more soluble in nonpolar solvents. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2536–2546, 2001

Polyelectrolyte effect in perfluorosulfonated ionomer solutions

Ubbelohde viscosity measurements were performed on dilute solutions of perfluorosulfonated ionomers (PFSI) in various solvents exhibiting quite different dielectric constants. With aliphatic alcohols as solvents an increase of the reduced viscosity with dilution is evident. This effect is analogous to the so-called ‘polyelectrolyte effect’ observed for highly charged ionic polymers in polar solvents. The polyelectrolyte effect increases with the dielectric constant for alcohols, is similar in water and in methanol solutions, and disappears for high polarity solvents. This evolution is discussed in terms of an increase of the electrostatic persistence length. The viscosimetric behaviour of PFSI solutions is shown to fit well with the Liberti-Stivala equation.

Rules for predicting vapor-liquid equilibria of amorphous polymer solutions using a modified Flory-Huggins equation

A method is proposed to predict solvent activities in amorphous polymer solutions. The method relies on two main assumptions: (i) the configurational entropie term of the excess Gibbs energy of mixing is adequately represented by the classical Flory-Huggins relation; (ii) the enthalpic term arising from the attractive interactions between the solvent molecules and the segments which constitute the polymer can be described by using the NRTL equation. To calculate the binary interaction parameters of the NRTL equation, the same strategy as previously adopted is followed to predict vapor-liquid equilibria of non-polymeric mixtures. Accordingly, literature experimental data are subdivided into the following classes of mixtures: — non-polar polymers in non-polar solvents — non-polar polymers in polar solvents — polar polymers in non-polar solvents — polar polymers in polar solvents For each of the above classes, simple rules are proposed which link the binary energy parameters of the NRTL equations to the difference between the Hildebrand solubility parameters of the polymer and the solvent. The proposed method is applied to over forty binary mixtures for which reliable data are found in the literature. A new procedure to calculate the Hildebrand solubility parameter of the polymer is also reported.

Solution properties of ion‐containing polymers in polar solvents

AbstractThe placement of ionic groups within the molecular structure of a polymer produces marked modification in physical properties. A large number of studies have been performed on these ion‐containing polymers, but few have focused on the effects of anion–cation interactions (i.e., counterion binding or ionization) on hydrodynamic volume, especially as the molecular structure of the solvent and nature of counterion are varied. In this study changes in hydrodynamic volume are followed through reduced viscosity measurements as a function of the abovementioned molecular parameters.The dilute solution properties of various polyelectrolytes that contain sulfonate and carboxylate groups were investigated as a function of the counterion structure, charge density, molecular weight, and solvent structure. The polymeric materials were selected because of their specific chemical structure and physical properties. In the first instance a (2‐acrylamide‐2 methylpropanesulfonic acid)‐acrylamide‐sodium vinyl sulfonate terpolymer was synthesized and subsequently neutralized with a series of bases. Viscometric measurements on these materials indicate that the nature of the cation affects the ability of the polyelectrolyte to expand its hydrodynamic volume at low polymer levels. The magnitude of the molecular expansion is shown to be due in part to the ability of the counterion to dissociate from the backbone chain, which, in turn, is directly related to the solvent structure. The changes in solution behaviour of these inomers lend support for the existence of ion pairs (i.e., site binding) and ionized moieties on the polymer chains. Measurements performed in a variety of solvent systems further confirm this interpretation. In addition, and acrylamide‐sodium vinyl sulfonate copolymer was partially hydrolyzed with sodium hydroxide to study the effect of varying the charge density at a constant degree of polymerization and counterion structure. The results show that the charge density has a significant effect on the magnitude of the reduced viscosity and dilute solution behaviour. These observations, made in aqueous and nonaqueous solvents, are related to the interrelation of hydrodynamic volume, counterion concentration, and site binding. Again the controlling factor is the degree of site binding of the counterion onto the polymer backbone. Finally, we observe that the increased hydrodynamic volume affects viscosity behavior beyond the polyelectrolyte effect regime. If the average charge density on the macromolecule is relative high and/or the molecular weight is large (≥ 106) sufficient intermolecular interactions will occur to produce rapid changes in reduced viscosity.

Synthesis and polymerization of vinyl esters and vinyl ethers having bulky substituents

AbstractIn order to clarify the effect of bulky substituents on the stereoregulation of vinyl monomers, vinyl‐1‐adamantanecarboxylate and vinyl 1‐adamantyl ether were synthesized and polymerized by radical and cationic mechanisms, respectively. As open‐chain models of the adamantyl group, vinyl trialkylacetate (alkyl = ethyl, n‐propyl, and n‐butyl) and vinyl tri‐n‐propylcarbinyl ether were also synthesized and polymerized. The adamantly group in the vinyl ester favored syndiotactic propagation in a manner similar to the trimethylcarbinyl group. Higher homologs of tri‐n‐alkylcarbinyl group showed higher syndiotacticity but this effect was saturated in higher members of the series. The effect of the adamantyl group in vinyl ether was similar to that of the tert‐butyl group, leading to high isotacticity on cationic polymerizations in nonpolar solvents and to atactic polymers in polar solvents, but the tri‐n‐propylcarbinyl group was found unique in leading to what was assumed to be a heterotactic polymer. Polymers with the adamantyl group showed much higher softening points than polymers of the corresponding open‐chain groups.