Side-chain functionalized liquid crystalline polymers and blends, 10: phase behavior and structure of side-chain liquid crystalline ionomers containing ions of d-metals

Novel side-chain liquid crystalline (LC) ionomers containing d-metals Co(II) and Ni(II) were synthesized and characterized. Both families of the ionomers are characterized by the same influence of charged group content in polymer on their phase behavior. The incorporation of 2-3 mol% of metal ions in the nematic polymer matrix leads to the induction of SmA phase and rise in the clearing point. The peculiarity of their phase behavior in comparison with the earlier investigated LC ionomers with alkaline or alkali-earth metals is the full destruction of the mesophase at the concentration of d-metal higher than 12 mol%. This phenomenon was associated with the well-known ability of the transition metal ions to form various complexes that, in the case of LC ionomers, can negatively influence the ordering of the side mesogenic groups. The proposed structure of the LC ionomers is discussed in comparison with the metallomesogenic polymer systems.     

High temperature shape memory polyimide ionomer

In this work, a high temperature shape memory polymer based on polyimide (PI) ionomer is prepared by introducing ionic crosslinked interaction. The ionic crosslinked points are introduced to polymer networks through the reaction between polyamic acid and calcium hydroxide before thermal imidization. The crosslinked reaction, microtopography, mechanical, thermal, and shape memory properties of PI ionomers are systematically investigated. The results show the introduction of ionic crosslinked interaction could enhance the glass transition temperature, mechanical, and shape recovery performance of ODA‐ODPA, a PI. The prepared ionomers exhibit good high temperature shape memory properties around 270 °C. The shape fixation and shape recovery ratio are over 99% and 90%, respectively. This method provided a new sight of preparing high temperature shape memory polymer, which could be used in severe conditions, like aerospace industry field. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43630.     

Formation of novel polymeric nanoparticles

We have found that not only block copolymers but also ionomers can self-assemble in a selective solvent to form surfactant-free nanoparticles. The self-assembly can be induced by chemical reaction, polymer-polymer complexation, and microphase inversion in addition to the temperature. A recently developed microwave method for the preparation of uniform surfactant-free polymeric nanoparticles is also reviewed. Our results have revealed that for a given dispersion, the particle surface area occupied per stabilizer (surfactant, polymer chains, and ionic groups) is close to a constant.     

Preparation and thermal properties of liquid crystalline ionomers having mesogenic ester side chains containing three phenyl groups

A series of liquid crystalline (LC) copolymers having both the repeat units of mesogenic ester side chains containing three phenyl groups and the repeat units possessing an acid group were prepared. The acid groups of the LC copolymers were neutralized with sodium acetate to give a varying degree of neutralization. It was found that the LC properties of the ionomers depended strongly on both the relative amount of the units having the mesogenic side chains and the amount of ionic units. It was also observed that the formation of the nematic phase of the LC ionomers was suppressed by the increase in ion contents. After the analysis of the thermal data of the phase transitions, it was suggested that the transition temperatures of the LC phases of the copolymers and their ionomer forms, and the temperature ranges for the LC phases were affected by the relative amounts of both mesogenic and acidic units and by the degree of neutralization, simultaneously.     

Yielding in ethylene/methacrylic acid ionomers

Ethylene/methacrylic acid (E/MAA) ionomers exhibit a complex morphology - consisting of polyethylene crystals, amorphous polymer segments and ionic aggregates - as well as pronounced differences in mechanical properties compared with the E/MAA copolymers from which they are derived. Here, we illuminate the microstructural origins of the changes in one such property - the yield stress - imparted to E/MAA by partial neutralization with sodium. The yield stress reflects contributions from both polyethylene crystal plasticity and incomplete mechanical relaxation of the ion-containing amorphous phase; the amorphous phase, in turn, consists of ion-rich aggregates and ion-poor domains, with widely separated relaxation rates. The inability of the amorphous material immediately surrounding the ionic aggregates to relax, except at extremely low strain rates, greatly increases the yield stress of the ionomers. Only a minor fraction of the E/MAA groups must be neutralized to create ion-rich aggregates, and thus to achieve the limiting yield stress behavior. The slow growth of thin polyethylene crystals also has a marked influence; as they form after quenching from the melt, these secondary crystals bridge the gaps between the locally-vitrified amorphous regions, leading to a large increase in yield stress.     

Novel polyimide ionomers: CO2 plasticization, morphology, and ion distribution

Aluminum crosslinked 6FDA-6FpDA:DABA 2:1 and 1:2 copolyimide membranes were synthesized and their CO₂-induced plasticization was investigated. The membranes are unstable against CO₂ plasticization in long-term permeation tests at 40 atm CO₂ feed pressure at 35 °C. To correlate the plasticization with the polymer morphology, scanning transmission electron microscopy (STEM) was used to image the ionomers. STEM shows Al-rich aggregates in both ionomers, but the aggregate size and shape distribution in the 1:2 film is much more heterogeneous than in the 2:1. The 1:2 ionomer contains spherical aggregates with diameters from ∼5 to 25 nm, chainlike assemblies of small spherical aggregates, vesicular aggregates, large distorted vesicular aggregates, and long band-like structures that extend up to 1000 nm in one dimension. The 2:1 ionomer only contains a few approximately spherical aggregates. Large fractions of both ionomers do not exhibit visible aggregates on the STEM length scale. IR spectroscopy reveals a neutralization level of the acid groups above 60% and transmission electron microscopy detects unreacted neutralizing agent in the polymer. Small angle and wide angle X-ray scattering patterns show scattering patterns that can be linked to the solid-state structure of the polymer backbone rather than the ionic aggregates.     

Main‐chain liquid‐crystalline ionomers bearing potassium sulfonate groups

A series of thermotropic main‐chain liquid‐crystalline (LC) ionomers were prepared, which contained potassium sulfonate groups pendent to the chains. The polymers were prepared in an esterifying reaction with potassium ion contents ranging between 0 and 3.9 wt %. The content of potassium ion was characterized by spectrophotometric analysis with sodium tetraphenylboron as the titrant. Chemical structures were determined by various experimental techniques including Fourier transform IR spectroscopy and ¹H‐NMR. LC properties were characterized by differential scanning calorimetry, polarizing optical microscopy, and X‐rays. All of the polymers displayed nematic or smectic mesophases. With increasing potassium sulfonate ionic concentration in the polymers, the melting temperatures and isotropic transition temperatures changed little, whereas the temperature of the smectic A–nematic phase transition increased. The ionic aggregation was tangled with the rigid mesogenic groups of LC segments to form multiple block domains, leading the soft main chains to fold and form a lamellar structure due to their electrostatic interactions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2021–2026, 2005     

Telechelic ionomeric poly(butylene terephthalate): Synthesis,characterization and comparison with random ionomers

Telechelic poly(butylene terephthalate) (PBT) ionomers have been prepared by melt synthesis using a new polycondensation process that involves a pre-reaction of sulfobenzoic acid sodium salt with butanediol. No side reaction occurs and the incorporation of the ionic groups is quantitative. The addition of a buffer agent, such as Na₃PO₄, to the catalyst reduces the THF formation and improves the polycondensation rate. The comparison of the thermo-mechanical and physical properties between random and telechelic ionomers is also reported. The ionic groups act as chain-extension reversible electrostatic links for telechelic ionomers while act as cross-links in random ionomers. Therefore, random ionomers present a consistently higher melt viscosity compared to telechelic ionomers and to PBT and for this reason high molecular weight random ionomers cannot be obtained by melt polycondensation. Thermal and hydrolytic stabilities of telechelic ionomers are comparable with those of commercial PBT and consistently higher respect to those of random ionomers. The presence of ionic groups decreases the translation mobility of the polymer chains thus lowering the crystallization rate.     

Silver- and Zinc-Decorated Polyurethane Ionomers with Tunable Hard/Soft Phase Segregation

Segmented polyurethane ionomers find prominent applications in the biomedical field since they can combine the good mechanical and biostability properties of polyurethanes (PUs) with the strong hydrophilicity features of ionomers. In this work, PU ionomers were prepared from a carboxylated diol, poly(tetrahydrofuran) (soft phase) and a small library of diisocyanates (hard phase), either aliphatic or aromatic. The synthesized PUs were characterized to investigate the effect of ionic groups and the nature of diisocyanate upon the structure–property relationship. Results showed how the polymer hard/soft phase segregation was affected by both the concentration of ionic groups and the type of diisocyanate. Specifically, PUs obtained with aliphatic diisocyanates possessed a hard/soft phase segregation stronger than PUs with aromatic diisocyanates, as well as greater bulk and surface hydrophilicity. In contrast, a higher content of ionic groups per polymer repeat unit promoted phase mixing. The neutralization of polymer ionic groups with silver or zinc further increased the hard/soft phase segregation and provided polymers with antimicrobial properties. In particular, the Zinc/PU hybrid systems possessed activity only against the Gram-positive Staphylococcus epidermidis while Silver/PU systems were active also against the Gram-negative Pseudomonas aeruginosa. The herein-obtained polyurethanes could find promising applications as antimicrobial coatings for different kinds of surfaces including medical devices, fabric for wound dressings and other textiles.     

New polymer electrolytes based on ether sulfate anions for lithium polymer batteries: Part I. Multifunctional ionomers: Conductivity and electrochemical stability

New lithium conducting ionomers based on commercial polyethers were synthesized by chemical modification in order to incorporate not only the anionic function on the polymer backbone but also polar aprotic and (or) protic groups improving both the salt dissociation and the anion-solvating ability of the multifunctional copolymers. The choice of environmentally friendly rather than perfluorinated anionic functions did not appear to compromise for the ionic conductivity. Lastly, the preliminary results on the use of an electrochemically stable and relatively cheap additive sparteine appear promising and could be generalized to a variety of polymer electrolytes for lithium batteries.     

侧链携带二茂铁基的聚N-异丙基丙烯酰胺与β-环糊精聚合物构成的可控超分子体系的研究

采用侧链携带二茂铁基的聚N-异丙基丙烯酰胺〔poly(NIPAM/FCN)〕及β-环糊精聚合物〔poly(-βCD)〕构成超分子体系。以核磁共振氢谱、循环伏安、粒径分析等手段对poly(-βCD)与poly(NIPAM/FCN)之间的主客体包结作用的研究表明,二茂铁聚合物poly(NIPAM/FCN)可与poly(-βCD)形成氧化还原可控超分子体系,并且该体系的溶液性能可以通过氧化反应来调节。     

Effect of organic amine type on the structure and properties of the complex Zn(II) salts of ethylene–methacrylic acid copolymer with organic amines

The complex Zn(II) salts of ethylene–methacrylic acid copolymer (EMAA) were synthesized by using various organic amines from monoamines to polyamines, from primary amines to tertiary amines, and from molecular amines to polymer amines. Thermal analyses by differential scanning calorimetry (DSC), and the measurement of stiffness, melt flow rate (MFR), and dielectric properties were employed for the complex salts. It was found that the valence, strength of base, rigidity and flexibility, and bulkiness of the organic amines affect the degree of crystalline order of the ionic crystallites, which governs the stiffness of the complex ion ionomers. The stiffness is higher for the complex salts which form the higher orderliness in the ionic aggregates. The organic amines with two or more primary aliphatic amino groups and higher boiling temperatures from more rigid ionic crystallites in the complex ion ionomers leading to the enhanced modulus. Monoamines or polyamines with amino groups attached to flexible chains such as polyether and polysiloxane scarcely develop ionic crystallites and preferentially solvate the amorphous region including ionic groups leading to the decreased modulus. These results provide us with the fundamental information to control the modulus of ionomers.     

A review of miscibility enhancement via ion-dipole interactions

It is shown that ion-dipole interactions induce considerable miscibility enhancement in blends of styrene ionomers with poly(alkylene oxides). Dynamic mechanical studies, in conjunction with transparency and brittleness of the samples, are used to evaluate miscibility. The effect is clearly thermodynamics in that phase separation can be induced in miscible samples by raising the temperature, with miscibility reestablished ons cooling. The miscibility enhancement in these systems is compared with that resulting from hydrogen bonding. In addition to the styrene/alkylene oxide system, ion-dipole interactions are found to be effective in enhancing the miscibility of many ionic polymer/polar polymer pairs. The ionomers used in this study were styrene lithium methacrylate and ethyl acrylate lithium acrylate copolymers, while polyethers, polysulfides, polyesters, polyimines, and substituted polyethylenses served as polar polymers.     

Ferrocene Redox Controlled Reversible Immobilization of Ruthenium Carbene in Ionic Liquid: A Versatile Catalyst for Ring‐Closing Metathesis

A ferrocene‐tagged ruthenium carbene 15 that can be reversibly immobilized in an ionic liquid (IL) via the controlled oxidation and reduction of a ferrocene tag was prepared. This offers a new strategy which uses redox chemistry to control immobilization and to recycle both the catalyst and the IL. In this experiment, 11 recycles were performed for the ring‐closing metathesis (RCM) of a substrate using 16 as the catalyst in an ionic liquid (IL). More importantly, after the reaction was completed, the ruthenium catalyst was easily separated from the supporting IL by just adding decamethylferrocene (DMFc) to reduce the cationic ferrocene and then extracting it with benzene. Thus, this recycle system offers an easy way to recycle both the ruthenium catalyst and the IL.     

Physicomechanical and dielectric properties of magnesium and barium ionomers based on sulfonated maleated styrene‐ethylene/butylene‐styrene block copolymer

Ionomers, containing both carboxylate and sulfonate anions on the polymer backbone, based on metal cations like Mg⁺² and Ba⁺² were prepared by sulfonating maleated styrene‐ethylene/butylene‐styrene block copolymer, hereafter referred to as m‐SEBS, followed by its neutralization by metal acetates. Infrared spectroscopic studies reveal that sulfonation reaction takes place in the para position of the benzene rings of polystyrene blocks and metal salts are formed on neutralization of the precursor acids. Dynamic mechanical thermal analyses show that sulfonation causes increase in T_g of the rubbery phase of m‐SEBS and decrease in tan δ at T_g of the hard phase, along with formation of a rubbery plateau. The changes become more pronounced on neutralization of the sulfonated maleated SEBS, and the effect is greater in the case of Ba salt. Dielectric thermal analyses (DETA) show that incorporation of ionic groups causes profound changes in the dielectric constant (ϵ′) of m‐SEBS. In addition to the low temperature glass–rubber transition, the plot of ϵ′ vs. temperature shows occurrence of a high‐temperature transition, also known as the ionic transition. Activation energy for the dielectric relaxation could be determined on the basis of frequency dependence of the ionic transition temperature. Two values of the activation energy for the dielectric relaxation refer to the presence of two types of ionic aggregates, namely multiplets and clusters. Incorporation of the ionic groups causes enhancement in stress–strain properties as well as retention of the properties at elevated temperatures (50° and 75°C), and the effect is more pronounced in the case of Ba ionomer. Although sulfonated ionomers show greater strength than the carboxylated ionomers, the sulfonated maleated ionomers show higher stress–strain properties in comparison to both sulfonated and carboxylated ionomers. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 816–825, 2000     

Imidazolium poly(butylene terephthalate) ionomers with long-term antimicrobial activity

Imidazolium poly(butylene terephthalate) ionomers with ionic groups located randomly along the polymer chain or selectively as end-groups (telechelic) have been prepared in order to determine their antimicrobial (AM) activity. Two different approaches have been followed for the linkage of the imidazolium to the polymer backbone: a covalent bond and an ionic aggregation to sulfonated groups covalently bonded to the polymer. The ionic groups have been linked to the polymer in order to improve the long-term AM activity since the low molecular weight additives commonly used tends to migrate toward the surface during use. We have found that imidazolium ionomers present AM activity comparable with that of commercial antimicrobial agents such as Triclosan. The AM activity depends on the polymer architecture, the telechelic approach being more active compared to the random approach. We have proved that imidazolium ionomers retain their high AM activity even after 6 days in water at 60 °C while Triclosan consistently loses his activity.     

Rheological properties of ethylene ionomer neutralized with binary metal cation

The roles of ionic bonding in molten ethylene ionomers without ionic aggregates were rheologically characterized in linear regions under shear. We have measured melt viscosities of ethylene-methacrylic acid (EMAA) ionomers by means of dynamic shear experiment. The samples used in this study were binary mixtures selected from Na, Mg and Zn salts of EMAA (MAA=5.4 mol%). The dynamic shear properties revealed that the time-material superposition is applicable to these ionomer blends in a temperature range from 140 to 200 °C. It was also found that these binary mixtures unexpectedly give decreases of zero shear viscosities obtained from a time-material superposition, if the cations were selected from different metal groups such as alkali, alkaline earth and transition metals. This behavior can be explained by the acid-cation exchange mechanism.     

Synthesis and characterization of imidazolium telechelic poly(butylene terephthalate) for antimicrobial applications

Poly(butylene terephthalate) ionomers with imidazolium groups selectively located as end-groups (telechelic) have been prepared by melt polycondensation adding a hydroxyl derivatized imidazolium salt at the beginning of the polymerization process. The design of the chemical structure of the imidazolium salt is of fundamental importance in order to achieve the synthesis of ionomers with good thermo-mechanical properties. The final ionomers present high molecular weight, good color, transparency and thermal stability. Imidazolium ionomers present good antimicrobial (AM) properties comparable with those of commercial AM agents. The incorporation of the ionic groups in the polymer chain prevents their migration during use and therefore the antimicrobial activity can be preserved for longer time.     

Untersuchungen zur Synthese und den Eigenschaften von amphiphilen Polymeren

Investigations of the Synthesis and Properties of Amphiphilic Polymers By reaction of propylene/maleic anhydride copolymers with the sodium salt of α-dodecyl-ω-hydroxy-trioxyethylene ionic polymers with different shares of long aliphatic side chains were prepared. The properties of these amphiphilic polymers were studied. Like micelles they are able to solubilize nonpolar probe molecules (N,N-dimethyl-aminoazobenzene). Viscosity measurements show the dependence of the conformation of the polymeric chain in solution on the share of aliphatic side chain and the degree of protonation. The polymers from micelle-like aggregates. It is supposed that the polymer with a high share of aliphatic side chains froms several local aggregates per polymer chain, while the polymer containing only few side chains seems to form intermolecular aggregates between different polymer chains. These investigations were performed with pyrene as probe molecule. Pyrene was also used to examine the micropolarity of the aggregates. Like polyelectrolytes the amiphilic polymers are able to cause the aggregation of opposite charged dyes (thionine).     

Toughening Rigid Epoxy Using Novel Potassium Silanolate Ionic Interactions

A rigid and densely cross‐linked epoxy resin is successfully toughened by introducing novel potassium silanolate ionic interactions, exhibiting simultaneous improvement in toughness, strength, modulus, and glass transition temperature. The ionic interactions are incorporated through a simple way into epoxy cured with a novel potassium silanolate ionic groups‐containing amine curing agent. Small angle X‐ray scattering/wide angle X‐ray scattering and dynamic thermomechanical analysis results show that the ionic groups aggregated into multiplets and clusters in the prepared epoxy ionomers. The temporary physical cross‐link effect of ionic aggregates and the consequently formed chain‐restricting ionomeric nanodomains account for the stiffening and toughening performance. Furthermore, the densely cross‐linked epoxy ionomers possess high stretchability at elevated temperature (about 800% at 200 °C) due to the dynamic ion‐hopping effect.