Size exclusion behavior of polymers in amide solvents

Summary The size exclusion chromatography of neutral polymers and polymers containing ionic groups was investigated using N,N-dimethylacetamide (DMA) as mobile phase. As reported previously for N,N-dimethylformamide (DMF), acrylonitrile polymers containing charges, even those at terminal end groups, showed markedly small retention volumes and multimodal peaks by refractive index and 280 nm UV detectors. In DMA containing small amounts of LiBr the peaks of the ionic polymers were shifted to small retention volumes while neutral polymers with analogous chemical structures did not show the same behavior. As in the case of DMF the peculiarities observed in DMA were attributed to the formation of supramolecular structures by the interaction of the ionic groups in the polymer and the ionic species from DMA decomposition.     

Salt effect on gel permeation chromatography of partially charged polymers

The effect of the addition of 0.1M LiBr to dimethylformamide (DMF) solutions of charged and uncharged polymers has been studied by GPC and [η] measurements. LiBr has a salting-out effect on polyacrylonitrile (with (PAN-S) and without (PAN) sulfonate sulfur), polystyrene (PS), and poly(vinyl acetate) (PVAc), which is seen by a decrease in [η] and an increase in the GPC retention time. The increase in retention time is, however, abnormally high for charged polymers. Association in PAN and PAN-S solutions in DMF can explain the experimental observations.     

Size exclusion chromatography of polyelectrolytes in dimethylformamide

A study of the size exclusion chromatographic behavior of styrene–methacrylic acid and epoxyacrylic polymers has been made. These polymers exhibit strong “ion-exclusion” effects in DMF, similar to that found for water-soluble polyelectrolytes such as sodium polystyrene sulfonate. The addition of lithium bromide, at a concentration of 0.1M, overcomes ion exclusion on a set of silicabased, “deactivated” duPont SEC columns. Calibration of both the duPont columns and a set of styrene–divinyl benzene based columns (μ-Styragel) is complicated by absorption of polystyrene standards in DMF and DMF/salt mobile phases. The absorption of monomeric solutes on the duPont columns in DMF/salt mobile phases is different from that of their corresponding polymers.     

Studies on polypyromellitimides containing phosphorus

The paper describes the synthesis of several polypyromellitimide samples containing phosphine oxide in the backbone and maleimido groups as pendant side chains. These polymers were obtained by solution polycondensation reaction in DMF in three steps. First step involved the reaction of equimolar amounts of maleic anhydride (MA) and tris(3-aminophenyl) phosphine oxide (TAP) in DMF at 60°C for 2 h. Low temperature polycondensation was carried out at 0–5°C by the addition of 4,4'-diaminodiphenyl ether (DADPE) and pyromellitic dianhydride. Cyclodehydration of poly(amide acid) thus obtained was done by chemical means. Various copolymers thus obtained were characterized by intrinsic viscosity measurements, elemental analysis, and IR spectroscopy. Thermal behavior and curing characteristics of copolyimides were evaluated by thermogravimetry and differential scanning calorimetric studies. An increase in the char yield at 800°C was observed on increasing phosphine oxide content of polyimides.     

Synthesis and characterization of new poly(butadiene-co-acrylic acid(g) acrylic acid) and poly(butadiene(g) acrylic acid)

Synthetic crosslinked polymers from oligomers of butadiene-co-acrylic acid (Mw 5000) or oligomers of butadiene (Mw 6000) and acrylic acids were obtained after grafting reactions using varying reactant ratios. Characterization of the new crosslinked polymers were carried out by use of FTIR, H-NMR, and ¹³C-NMR in the solid state and also with the swollen products in D₂O, DMF D7, or DMSO D6. Determinations of swelling in distilled water for the different synthesized hydrogels showed increase in the V/Vo ratios as the concentrations of anions (carboxylate) became higher. These values were sensitive to different pH values and changes in the concentrations of electrolytes. Different behavior was observed for the polymers obtained from mass and from synthesis in benzene. SEM analysis of the surfaces of the polymers obtained in mass showed a fibrous structure (with lower contents of carboxylic groups, and more swellable and with greater capacity to retain albumin). A porous surface was observed for products obtained in benzene (with higher content of carboxyl groups and capacity to retain cations such as copper and malachite green).     

15th anniversary of polymerised ionic liquids

Polymerised ionic liquids (PILs) have unique properties such as low glass transition temperature (Tg) in spite of very high charge density. Due to these advanced points, PILs have been prepared and initially evaluated as ion conductive polymers. Progress of low-Tg polyelectrolytes has been previously demonstrated with polyethers having charged end(s) as a kind of PILs. Then, imidazolium-type ionic liquids (ILs) were polymerised after introducing vinyl groups onto the imidazolium cation rings. It is reasonable that the ionic conductivity of thus prepared PILs decreased due to elevation of Tg and decrease of the number of mobile small ions. Efforts were then paid to suppress drop of ionic conductivity after polymerisation. Variety of PILs has been improved to show excellent ionic conductivity, selective ion transport, and other properties. With the progress of functional ILs, some functions were also added to PILs which cannot be realised with ordinary charged polymers. In the present mini-review, we briefly introduce history of a variety of polymerised ILs and some applications of these PILs.     

Permeation behavior of dextrans by charged ultrafiltration membranes of polyacrylonitrile photografted with ionic monomers

Charged copolymers, polyacrylonitrile, having grafts of quaternized poly(N,N-dimethylaminoethylmethacrylate) and poly(sodium p-styrenesulfonate), were synthesized by photograft-polymerization. The charged ultrafiltration membranes, which had heterogeneous porous structures, were prepared by casting graft polymer solution containing poly(vinyl alcohol) into water. The permeation of nonionic dextran and anionic dextransulfate through the charged membranes was studied by ultrafiltration in aqueous solution. The molecular weight cutoff characteristics of the charged membrances were obtained using dextrans of various molecular sizes. The permeation behavior was discussed in terms of the charge effect of the graft polymers and electrostatic interaction between the polymers and the solute molecules.     

Polyelectrolyte behavior of chemically modified cotton cellulose

Ion exchange and sorption of charged molecules such as dyes, crosslinking agents, etc., by cotton cellulose very much depend on the charge on cellulose, which in turn is known to depend on the external pH of the medium. In order to understand the role of various fixed groups in cellulose in its polyelectrolyte behavior, the standard cellulose was deliberately oxidized with nitrogen dioxide and sodium periodate, and the sorption of formaldehyde and dimethylol dihydroxyethylene urea by these oxycelluloses as well as by alkali-treated nitrogen dioxide–oxycellulose was investigated. The results obtained are interpreted in terms of polyampholyte behavior of oxycellulose. The nitrogen dioxide–oxycellulose is positively charged and is a polycation in acidic medium due to protonation of aldehyde groups while it is negatively charged and acts as a polyanion in slightly acidic to alkaline medium due to dissociation of carboxyl groups.     

Bioerodible hydrogels based on 2‐hydroxyethyl methacrylate: Synthesis and characterization

Biocompatible polymers with specific shape and tailored hydrogel properties were obtained by polymerization of mixtures of 2‐hydroxyethyl methacrylate (HEMA) with 1–8 wt % ethylene glycol dimethacrylate (EGDMA) or tetra(ethylene glycol) diacrylate (TEGDA) as crosslinking agents, by using a redox initiator. Introduction of charged positive and negative groups was easily achieved by direct polymerization of appropriate monomer mixtures and by chemical transformation of preformed hydrogels. Investigation of the swelling behavior of the prepared hydrogels evidenced an appreciable dependence on both solvent type and polymer chemical structure. Additionally, the solvation process resulted in being controlled by solvent diffusion, according to a Fickian II mechanism. The presence of several types of water with different melting behavior was observed in fully swollen hydrogels. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2729–2741, 2002     

Interactions between anionically modified hydroxyethyl cellulose and cationic surfactants

Macroscopic properties of aqueous solutions of several modified hydroxyethyl cellulose (HEC) samples and their interactions with cationic surfactants are studied by solubility, light scattering, electric birefringence, rheology, and surface tension measurements. Modified HEC samples carry anionic groups (an-HEC D0) and anionic and hydrophobic groups in random distribution (HM-an-HEC D1–D4). The molar substitution of anionic (an) groups is about 0.07 in all samples while that of the hydrophobic (HM) groups ranges from 0 in an-HEC D0 to 0.012 in HM-an-HEC D4. In a 1 wt% solution this corresponds to 2.7 mM anionic and 0 to 0.46 mM hydrophobic groups. In the dilute concentration range the polymers behave like typical polyelectrolytes whereas in the semi-dilute range they resemble uncharged polymers. On addition of oppositely charged surfactants the phase behavior of all polyelectrolytes is similar. With increasing surfactant concentrations the transparent solutions become turbid and the phases separate. Finally, resolubilization takes place with excess surfactant concentrations. With the HM-an-HEC compounds viscoelastic solutions are formed with cationic surfactants. The intermolecular interaction between hydrophobic parts of the polymers and the surfactants and interactions of oppositely charged ionic groups of the two components lead to formation of a temporary network with gel-like properties. With an-HEC the interaction can only take place via charges. Viscosity enhancement with increasing surfactant concentration is therefore lower with an-HEC than with HM-an-HEC compounds.     

Polyimides 7: Synthesis,characterization, and properties of novel soluble semifluorinated poly(ether imide)s

Three novel diamine monomers ( VI , VII , and VIII ) were synthesized. These diamine monomers lead to a number of semifluorinated poly(ether imide)s when reacted with different commercially available dianhydrides like pyromellitic dianhydride (PMDA), benzophenone tetracarboxylic acid dianhydride (BTDA), 2,2‐bis (3,4‐dicarboxyphenyl) hexafluoropropene (6FDA), and oxydiphthalic dianhydride (ODA) by thermal imidization route. Elemental analyses, IR and NMR techniques were used to characterize the monomers and polymers. The resulting polymers exhibited weight average molar masses up to 1.78 × 10⁵ g mol^?1 in GPC with respect to polystyrene standard and have very good solubility in several organic solvents such as NMP, DMF, DMAC, DMSO, chloroform, and THF. Very good solubility of these polymers in CDCl₃ enables their complete characterization by proton as well as ¹³C‐NMR techniques. The polymers showed very high thermal stability with decomposition temperature (5% weight loss) up to 511°C in air and high glass transition temperature up to 311°C depending upon the exact repeating unit structure. The polymer films showed high modulus (up to 2.9 GPa) as was evaluated by DMA. The polymers also showed very low water absorption (0.16%), low dielectric constant (2.35 at 1MHz) and very good optical transmission. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3025–3044, 2007     

Synthesis and properties of chelate polymers of VO(II), Mn(II), Zn(II), Fe(III), and Cr(III) with schiff base of 5,5′-methylene bis-salicylaldehyde with aniline

Polychelates of VO(II), Mn(II), Zn(II), Fe(III), and Cr(III) were prepared from Schiff base of 5,5′-methylene bis-salicyladehyde with aniline. All the chelate polymers are amorphous and insoluble in common organic solvents. They have very little solubility in DMF. The first three polychelates are found to be noncharged chelate polymers while the last two polychelates are found to be ionic from their conductivities in DMF. Their probable structures were determined from reflectance electronic spectral and magnetic measurements in conjunction with infrared measurements. The thermal stability, order of reaction and activation energy for all the polychelates were determined from their thermogravimetric analyses.     

电场作用下荷电膜对多糖溶液的超滤性能

以分子量小于10000的右旋糖苷硫酸酯为分离对象，通过膜通量、截留率、膜通量衰减程度和膜的清洗恢复率等参数的测定，考察了外加直流电场作用下荷电超滤膜的分离性能。结果表明：与中性膜PES300相比，外加电场下荷电膜的膜通量和截留率都有所提高，而膜通量衰减程度由41．86％分别降低到19．51％和13．28％。结合使用膜改性和外加电场两种强化方法，膜的衰减程度可进一步降至8．33％，而且使用过的荷电膜清洗后其膜通量的恢复率可达到95％，表明能较大地改善膜的抗污染性能。     

Synthesis,characterization, and studies on the solid-state crosslinking of functionalized vinyl cinnamate polymers

Functionalized vinyl cinnamate monomers were synthesized by the reaction between hydroxyethylacrylate (HEA) and substituted cinnamoyl chlorides possessing electron releasing and withdrawing functional groups like chloro, methoxy, and nitro groups at the para position of the aromatic ring. The structures of these monomers were characterized by Fourier transform infrared (FTIR), ¹H-, and ¹³C-NMR spectral techniques. The homopolymers of the synthesized monomers were obtained by the free radical solution polymerization in dimethylformamide (DMF) at 80°C for 12 h using azobisisobutyronitrile (AIBN) as a radical initiator. The sensitivity of these polymers towards light was studied by monitoring the photocrosslinking nature of the polymers by ultraviolet (UV) and FTIR techniques. The effect of the functional groups on the crosslinking efficiency was studied and compared with that of the unsubstituted polymer. The cyclobutane-type addition mechanism involved in the photocrosslinking phenomena was confirmed by the above spectral studies in the functionalized vinyl cinnamate polymers. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 441–448, 1998     

Redox-active liquid-crystalline ionomers: 1. Synthesis and rheology

Liquid-crystalline (LC) copolymers with redox-active groups were prepared by copolymerization of mesogenic and ferrocene-containing monomers (up to 10%). In these copolymers the ferrocene groups can be oxidized reversibly to prepare ionomers, while retaining the LC phase. It is thus possible to vary the amount of ionic groups in the ionomers by a redox reaction. The oxidized (charged) polymers show a strong excess X-ray scattering at small angles. This is typical for ionomers and is assigned to the scattering of ionic aggregates. Dynamic mechanical measurements show that these aggregates are effective as crosslinking points. Thus an oxidation-reduction reaction can be used to transfer an uncrosslinked polymer (reduced ferrocene groups, uncharged) reversibly into an oxidized polymer that acts like a weakly crosslinked gel.     

Graft copolymerization of glass fiber and its application

Modified glass fibers, containing unsaturated hydrocarbon surface groups, were prepared by a hydrothermal treatment, with allylglycidylether in excess as reagent. Graft polymerization of the treated glass fiber with styrene and methylmethacrylate was carried out in sealed tubes, under nitrogen, using benzoyl peroxide (BPO) and cumene hydroperoxide (CHPO) as initiators. When BPO was used as the initiator, the grafting efficiency was extremely low, but the graft copolymerization behavior was similar to that of usual organic polymers. With CHPO, both grafting ratio and grafting efficiency were very high. Various properties of composite materials containing grafted glass cloth were studied. Flexural strength, flexural modulus, and interlaminar shear strength increased proportionally to the increase of the grafting ratio; the same values were decreased only in a small extent after the boiling test.     

Processing behavior of polycarbonate/functionalized‐ethylene copolymer blends

The melt blending of polycarbonate (PC) and ethylene‐methacrylic acid copolymers (EFC) either in the acid form (EFC‐H) or partially neutralized with sodium (EFC‐Na) or zinc (EFC‐Zn) was investigated. Torque monitoring of the blending showed that the polymers are capable of reacting generating new chemical species that increase the melt viscosity. As general behavior, the torque curves pass by a maximum that takes place before 30 min, the final torque being higher than that of the individual polymers. SEC analyses reveal that PC degradation also occurs and is stronger in the case of blends with EFC‐Na that acts to catalyze PC degradation, promoting CO₂ formation. FTIR studies on chloroform insoluble fractions of the PC/EFC‐Zn blends showed that in addition to a very small number of carbonate groups, feature absorption bands of aromatic ester and hydroxyl groups appear in the new chemical species formed during the reactive processing.     

Diacetylene-containing polymers. XI. Synthesis and characterization of poly(hexa-2,4-diynylene-1,6-dioxydibenzoate) and poly(octa-3,5-diynylene-1,8-dicarboxylate) containing p-nitroaniline groups

Summary Two novel polymers containing p-nitroaniline group in the side chain and diacetylene groups in the main chain, were synthesized, and characterized. The polymers gave films of excellent optical quality by spin coating from DMF or chloroform. The one containing benzoate had a T_g of 103°C and its thermal cross-linking through the diacetylene group started at around 160°C. The one containing pentynoate had a T_g of 35°C and its cross-linking started at around 120°C. It was shown that thermosetting resins with functional groups could be obtained by using diacetylene-containing polymers. Although these two polymers have a same polar dye molecule, the second order nonlinear optical property was so different, showing that the main chains are very important for nonlinear optical property. Irradiation of UV light converted the polymer films to completely insoluble thermoset resins. Received: 13 February 2001/Revised version: 25 July 2001/Accepted: 30 July 2001     

Synthesis and properties of sulfonated aromatic fluoro‐polymers

Polycondensation of perfluorobiphenyl with α,α‐bis(4‐hydroxyphenyl)ethylbenzene and/or 9,9‐bis(4‐hydroxyphenyl)fluorene was investigated. The polycondensation of perfluorobiphenyl with α,α‐bis(4‐hydroxyphenyl)ethylbenzene and/or 9,9‐bis(4‐hydroxyphenyl)fluorene proceeded at low‐temperature to a give high‐molecular weight and thermal stable polymers. The ¹⁹F‐NMR spectra of the polymers indicate that the polymers consists of predominantly 1,4‐phenylene structure with respect to the perfluoro‐aromatic compound. The sulfonation of the polymers obtained from the polycondensation occurred at the phenyl groups and fluorenyl side chain. A tough and smooth film was prepared by a casting method from DMF solution of the sulfonated polymer. The films showed hydrolytic and oxidative stabilities, and a high‐proton conductivity. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Influence of molecular structure on the degradation mechanism of degradable polymers: In vitro degradation of poly(trimethylene carbonate), poly(trimethylene carbonate-co-caprolactone), and poly(adipic anhydride)

Relationships between molecular structure and the degradation mechanism of degradable polymers are of special interest for temporary medical applications. The in vitro degradation study of three aliphatic polymers—poly(trimethylene carbonate) (PTMC), poly(trimethylene carbonate-co-caprolactone) (PTMC-PCL), and poly(adipic anhydride) (PAA)—revealed that these polymers exhibit degradation times from several years (PTMC) to 1 day (PAA). PTMC degraded unexpectedly slow, accompanied by very small changes in weight loss, molecular weight (SEC), and in morphology (DSC, SEM). The degradation was independent of initial molecular weight, ionic strength of the water solution, temperature, and shaking motions. The copolymer PTMC-PCL showed a higher degradation rate compared to PTMC, with preferential degradation of amorphous parts leading to an increase in % crystallinity. The surprisingly rapid degradation of PAA showed characteristics typical for a surface-like eroding system in contrast to PTMC and PTMC-PCL. The degradation products corresponded to the repeating unit of the polymers. The hydrolysis rate increases in the order carbonate, ester, anhydride, and by combining different molecular structures we achieve specific degradation behavior. A change in hydrolysis rate of the labile bond is predicted by altering the electronegativity of groups near the carbonyl-oxygen region. © 1995 John Wiley & Sons, Inc.