Probing the effect of anion structure on the physical properties of cationic 1,2,3‐triazolium‐based poly(ionic liquid)s

To extensively explore the influence of anion structure on the physical properties of poly(ionic liquid)s (PILs) a series of PILs having main‐chain 1,2,3‐triazolium cations was synthesized via copper(I)‐catalyzed azide‐alkyne 1,3‐dipolar cycloaddition (CuAAC) followed by N‐alkylation with iodomethane and anion metathesis with different metal salts, that is, Li(CF₃SO₂)₂N, Li(CF₃CF₂SO₂)₂N, K(FSO₂)₂N, K(CF₃SO₂)N(CN), Ag(CN)₂N, and sodium 4,5‐dicyano‐1,2,3‐triazolate. To isolate the effect of anion on physical properties of PILs, a common iodide precursor was used to maintain constant the average degree of polymerization (DP_n) and chain dispersity. Detailed structure/properties relationship analyses demonstrated a lack of correlation between anion chemical structure, ionic conductivity, and glass transition temperatures. Among synthesized series, the PIL derivative having bis(trifluoromethylsulfonyl)imide counter anion showed the best compromise in performance: low glass transition temperature (T_g = ?68 °C), high thermal stability (T_onset = 340 °C) and superior ionic conductivity (σ_DC = 8.5 × 10^{? 6} S/cm at 30 °C), which makes it an interesting candidate for various key modern electrochemical applications. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2191–2199     

Accelerated Solvent‐ and Catalyst‐Free Synthesis of 1,2,3‐Triazolium‐Based Poly(Ionic Liquid)s

A straightforward and expeditious monotopic approach for the preparation of 1,2,3‐triazolium‐based poly(ionic liquids) (TPILs) is reported. It is based on the solvent‐ and catalyst‐free polyaddition of an α‐azide‐ω‐alkyne monomer in the presence of methyl iodide or N‐methyl bis[(trifluoromethyl)sulfonyl]imide alkylating agents. Poly(1,2,3‐triazole)s generated in bulk or by thermal azide–alkyne cycloaddition (AAC) are quaternized in‐situ to afford TPILs composed of 1,3,4‐ and 1,3,5‐trisubstituted 1,2,3‐triazolium units. The physical and ion‐conducting properties of the prepared samples are compared with the TPILs composed solely of 1,3,4‐trisubstituted 1,2,3‐triazolium units obtained through a multistep approach involving copper(I)‐catalyzed AAC polyaddition, quaternization of the 1,2,3‐triazole groups, and anion metathesis. TPILs obtained through the monotopic approach display thermal stabilities and ionic conductivities comparable to their pure regioisomeric analogues.

     

Nanohybrids based on polymeric ionic liquid prepared from functionalized MWCNTs by modification of anionically synthesized poly(4‐vinylpyridine)

We report the synthesis of a composite material comprised of poly(4‐vinylpyridine) (P4VP) grafted on multiwall carbon nanotubes (MWCNTs) and the preparation of a nanohybrid via quaternization of the nitrogen atom per monomeric unit of the polymer chains. 4‐Vinylpyridine was polymerized anionically using high vacuum techniques and was reacted with MWCNTs under vacuum to be grafted on the polymer segments. The composite material was soluble in common solvents and the dispersion of the carbon nanotubes was improved after quaternization due to the formation of polymeric ionic liquid (PIL) of the MWCNTs‐g‐[P4VP‐r‐poly(4ViEtPy⁺Br^‐)] type. The successful synthesis was confirmed with Fourier‐transform infrared and Raman spectroscopies, whereas differential scanning calorimetry was adopted to verify the stability of the polymer's glass transition temperature before and after grafting on the MWCNTs. Moreover, thermogravimetric analysis was used for examining the thermal stability and the PIL formation of the composite. Energy dispersive spectroscopy measurements confirm the precipitation of silver bromide when the MWCNTs‐g‐[P4VP‐r‐poly(4ViEtPy⁺Br^‐)] is reacted with silver nitrite indicating the successful quaternization and formation of the appropriate PIL. High temperature size exclusion chromatography was used for the determination of the molecular characteristics (average molecular weight by number $\overline M _n$ , polydispersity I) of the homopolymer obtained from the filtration of the composite material. Finally, field‐emission scanning electron microscopy was used to verify the successful grafting of the polymer to the MWCNTs. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Side chain liquid crystal poly(fumarate)s bearing tolane‐based mesogens

Cyanotolane or fluorotolane mesogens were for the first time introduced into the fumarate monomer under basic conditions. All fumarate monomers undergo radical polymerization in benzene in the presence of dimethyl 2,2′‐azobis(isobutyrate) as an initiator at 60 °C, affording the corresponding poly(fumarate)s with a molecular weight (M_n) of ～ 10⁴ and an exceptionally narrow polydispersity. The phase behaviors of the fumarate monomers and the correspoding poly(fumarate)s were comprehensively investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X‐ray diffraction (XRD) analysis. For the fumarate monomers, fluorotolane derivatives were prone to form higher‐order liquid crystal phases such as a smectic phase, while cyanotolane derivatives tended to show a wide mesophase temperature range, depending on the alkyl chain spacer length. Very surprisingly, these features dramatically weakened when they were polymerized. The mesophase temperature ranges became narrow and completely disappeared for the poly(fumarate)s with a shorter alkyl chain spacer. A nematic phase representing lower‐order arrangements became a predominant liquid crystal phase for the poly(fumarate) carrying cyanotolane mesogens. Only the poly(fumarate) carrying fluorotolane mesogens with a longer alkyl chain spacer displayed the characteristic XRD patterns of the smectic B phase. The transient photocurrent measurements of the fumarate monomer with cyanotolane mesogens displayed a hole mobility of the order of 10^?4–10^?5 cm² V^?1 s^?1 at room temperature. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5101–5114, 2008     

Solving the loss of orthogonality during the polyaddition of α‐azide‐ω‐alkyne monomers catalyzed by Cu(PPh3)3Br: Application to the synthesis of high‐molar mass polytriazoles

Polyaddition of an α‐azide‐ω‐alkyne monomer by Cu(PPh₃)₃Br catalyzed 1,3‐dipolar cycloaddition was thoroughly studied as a model system to investigate the orthogonality of this click chemistry process. Indeed, loss of chain‐end functionality and occurrence of side reactions have a tremendous impact on the molar mass of polymers obtained by step growth polymerization. Particularly, SEC, ¹H, and ³¹P NMR experiments have highlighted the occurrence of a Staudinger side‐reaction between azide chain‐ends and PPh₃ from the copper(I) catalyst that dramatically alters M_n of the resulting polytriazoles. A significant enhancement of M_n could be achieved by using an alternative catalyst and optimized experimental conditions, that is, dilution and reaction time. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2470–2476, 2010     

Fast and reversible CO2 quartz crystal microbalance response of vinylimidazolium‐based poly(ionic liquid)s

A series of poly(ionic liquid)s (pILs) based on the 1‐vinyl‐3‐hexylimidazolium polymerizable cation and on the bis(trifluoromethylsulfonyl)imide, nonafluoro‐1‐butanesulfonate, dodecylbenzenesulfonate, heptadecafluorooctanesulfonate, and 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11‐heptadecafluoroundecanoate anions have been synthesized and characterized. Their sorption/desorption response towards CO₂ has been tested through quartz crystal microbalance investigations. The obtained results show that all of the pILs here reported are featured by peculiar CO₂ sorption properties as they display fast and linear response, reversibility without any memory effect, and reproducibility, suggesting that anion plays a key role in determining sensitivity. Copyright © 2011 John Wiley & Sons, Ltd.     

Calorimetric and Dielectric Study of the Segmented Biodegradable Poly(ester‐urethane)s Based on Bacterial Poly[(R)‐3‐hydroxybutyrate]

Two series of segmented poly(ester‐urethane)s were synthesized from bacterial poly[(R)‐3‐hydroxybutyrate]‐diol (PHB‐diol), as hard segments, and either poly(ε‐caprolactone)‐diol (PCL‐diol) or poly(butylene adipate)‐diol (PBA‐diol), as soft segments, using 1,6‐hexamethylene diisocyanate as a chain extender. The hard‐segment content varied from 0 to 50 wt.‐%. These materials were characterized using ¹H NMR spectroscopy and GPC. The polymers obtained were investigated calorimetrically and dielectrically. DSC showed that the T_g of either the PCL or PBA soft segments are shifted to higher temperatures with increasing PHB hard‐segment content, revealing that either the PCL or PBA are mixed with small amounts of PHB in the amorphous domains. The results also showed that the crystallization of soft or hard segments was physically constrained by the microstructure of the other crystalline phase, which results in a decrease in the degree of crystallinity of either the soft or hard segments upon increase of the other component. The dielectric spectra of poly(ester‐urethane)s, based on PCL and PHB, showed two primary relaxation processes, designated as α_S and α_H, which correspond to glass–rubber transitions of PCL soft and PHB hard segments, respectively. Whereas in the case of other poly(ester‐urethane)s, derived from PBA and PHB, only one relaxation process was observed, which broadens and shifts to higher temperature with increasing PHB hard‐segment content. It was concluded from these results that our investigated materials exhibit micro‐phase separation of the hard and soft segments in the amorphous domains.     

Novel imidazolium‐based poly(ionic liquid)s: preparation,characterization, and absorption of CO2

The development of novel materials for carbon dioxide (CO₂) capture is of great importance in resource utilization and environmental preservation. In this study, imidazolium‐based ionic liquids (ILs) with symmetrical ester and hydroxyl groups were prepared, and their corresponding polymer were synthesized by melt condensation polymerization. The structure and properties of the poly(ionic liquid)s (PILs) were characterized by proton nuclear magnetic resonance, gel permeation chromatograph, differential scanning calorimetry, X‐ray diffraction, and scanning electron microscopy. In addition, the CO₂ sorption behavior of the IL monomers and PILs were studied at a low pressure (648.4 mmHg CO₂) and under a temperature of 25°C using a thermogravimetric analyzer. The CO₂ sorption capacity of 1,3‐bis(2‐hydroxyl ethyl)‐imidazolium hexafluorophosphate ([HHIm]PF₆, 10 mol%) was the highest among all the IL monomers and PILs studied. This capacity is also much higher than those reflected of previously reported ILs. Moreover, the sorption equilibrium of [HHIm]PF₆ was achieved within a short time. Copyright © 2011 John Wiley & Sons, Ltd.     

Poly(ionic liquid)s derived from 3‐octyl‐1‐vinylimidazolium bromide and N‐isopropylacrylamide with tunable properties

A new series of linear and crosslinked copolymers, obtained from 3‐octyl‐1‐vinylimidazolium bromide (VImBr) and N‐isopropylacrylamide (NIPAAm), were prepared by radical polymerization. Namely, VImBr was synthesized from 1‐bromooctane and an ionic liquid such as 1‐vinylimidazole. NIPAAm was used because it gives raise to well known thermoresponsive (co‐)polymers. The copolymers were thoroughly characterized by means of ¹H NMR and ¹³C NMR spectroscopies. Besides, differential scanning calorimetry, Fourier transform infrared spectroscopy, and scanning electron microscopy were also used. Moreover, the swelling behavior and the thermoresponsive properties of the corresponding hydrogels were studied. It was found that the VImBr incorporation into the copolymers does have a dramatic influence on both the thermal properties of the dried materials and the lower critical solution temperature of the corresponding hydrogels. In detail, the glass transition temperature was dependent on the monomer ratios, and ranged from 5 to 155 °C. Analogously, the lower critical solution temperature of the resulting hydrogels ranged from less than 10 up to 38 °C, thus including the physiological temperature. NMR spectroscopies, which were performed on the linear polymers, indicated that the monomers exhibit an alternating tendency resulting in a microstructure in which blocks are not present, at least when the two monomers are in equimolar amounts. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3521–3532     

Polymerization of methyl methacrylate by 2‐pyrrolidinone and n‐dodecyl mercaptan

The bulk polymerization of methyl methacrylate initiated with 2‐pyrrolidinone and n‐dodecyl mercaptan (R‐SH) has been explored. This polymerization system showed “living” characteristics; for example, the molecular weight of the resulting polymers increased with reaction time by gel permeation chromatographic analysis. Also, the polymer was characterized by Fourier transform infrared spectroscopy, ¹H NMR, and ¹³C NMR techniques. The polymer end with the iniferter structures was found. By the initial‐rate method, the polymerization rate depended on [2‐pyrrolidinone]^1.0 and [R‐SH]⁰. Combining the structure analysis and the polymerization‐rate expression, a possible mechanism was proposed. n‐Dodecyl mercaptan served dual roles—as a catalyst at low conversion and as a chain‐transfer agent at high conversion. Finally, the thermal properties were studied, and the glass‐transition temperature and thermal‐degradation temperature were, respectively, 25 and 80–100 °C higher than that of the azobisisobutyronitrile system. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3692–3702, 2002     

Synthesis and characterization of new segmented polyurethanes with side‐chain,liquid‐crystalline chain extenders

Liquid‐crystalline, segmented polyurethanes with methoxy–biphenyl mesogens pendant on the chain extender were synthesized by the conventional prepolymer technique and esterification reaction. Two, side‐chain, liquid‐crystalline (SCLC) polyurethanes with mesogens having spacers of six and eight methylene units were prepared. The structures of the mesogenic units and SCLC polyurethanes were confirmed by Fourier transform infrared spectroscopy and ¹H NMR. Polymer properties were also examined by solubility tests, water uptakes, and inherent viscosity measurements. Differential scanning calorimetry studies indicated that the transition temperature of the isotropic to the liquid‐crystalline phase decreased with increasing spacer length. Wide‐angle X‐ray diffraction (WAXD) studies revealed the existence of liquid‐crystalline phases for both SCLC polyurethanes. Polarized optical microscopic investigations further confirmed the thermotropic liquid‐crystalline behaviors and nematic mesophases of both samples. Thermogravimetric analysis displayed better thermal stabilities for both SCLC polymers and indicated that the presence of mesogenic side chains may increase the thermal stability of segmented polyurethanes. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 290–302, 2004     

Thermotropic liquid‐crystalline poly(oxadiazole)s with poly(methylene) spacers: Preparation and extraordinary odd–even effect

A novel synthetic procedure for the preparation of poly(oxadiazole)s was developed with nucleophilic substitution of α,ω-alkanediols with oxadiazole-activated bisfluoride. Seven poly(oxadiazole)s were successfully prepared by the solution polymerization of 2,5-bis(4-fluorophenyl)-1,3,4-oxadiazole and various α,ω-alkanediols [HO (CH₂)_n OH, n = 5–10 or 12] in diphenyl sulfone at temperature greater than 230 °C with K₂CO₃ as a catalyst. The reduced viscosities of the poly(oxadiazole)s were 0.14–0.51 dL/g, and the decomposition temperatures were greater than 350 °C and decreased from 436 to 379 °C with increasing spacer length (n). Corresponding model compounds, consisting of two terminal mesogenic 2,5-bisphenyl-1,3,4-oxadiazole units and central poly(methylene) spacers, were also prepared for comparison. Both the polymers and model compounds exhibited an extraordinary odd–even effect: odd ones showed higher transition temperatures (melting and clearing temperatures). With differential scanning calorimetry, polarized optical microscopy (POM), and X-ray diffraction, we found that the nematic mesophase was the only texture in the melts except for the polymers with longer methylene units (n = 9), in which smectic mesophases were observed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 293–301, 2002     

Ionic liquids as novel and green media for clean synthesis of soluble aromatic‐aliphatic poly(amide‐ester)s containing hydroxynaphthalene urazole moiety

Ionic liquids (IL)s are very attractive and environmentally acceptable solvents. They can be used as green media for a number of chemical processes. In this investigation, for the advancement of ecological safety and improvement of technological ability of this process, room temperature ionic liquids (RTIL)s and quaternary ammonium salt, tetrabutylammonium bromide (TBAB) have been used both as an environmentally benign solvent and catalyst for the polycondensation 4‐(3‐hydroxynaphthalene)‐1,2,4‐triazolidine‐3,5‐dione ( 3HNTD ) with aliphatic diacid chlorides, eliminating the need for a volatile organic solvent (VOS) and additional catalyst. The reaction of monomer 3HNTD with acetyl chloride was performed in N,N‐dimethylacetamide solution at different molar ratios, and the resulting mono‐, di‐, and trisubstituted derivatives were obtained in high yields and were finally used as models for polymerization reactions. The effects of various reaction parameters, such as the nature of the ILs, the amount of ILs, the reaction temperature, and the reaction time, on the yields and inherent viscosities of the resulting poly(amide‐ester)s (PAE)s were studied. Polycondensation reactions successfully proceeded in IL without any additional extra components, such as triethylamine or pyridine, which are used in similar reactions in organic solvents. Therefore, ILs can act both as solvent and catalyst. In addition to the solubility test, inherent viscosity as a measure of molecular weight was determined. PAEs were obtained in high yields with inherent viscosities ranging from 0.18 to 0.34 dl g^?1. This method was also compared with conventional method for the synthesis of PAEs. Fluorimetric studies of the model compound as well as polymers were performed. Copyright © 2008 John Wiley & Sons, Ltd.     

Promoting effect of thiophenols on the ring‐opening polymerization of 1,3‐benzoxazine

Thiophenol and p‐nitrothiophenol were evaluated as promoters for the ring opening polymerization of benzoxazine. The ring‐opening polymerization of p‐cresol type monofunctional N‐phenyl benzoxazine 1a with 10 mol % of thiophenols proceeded at 150 °C, leading to the high conversion of 1a more than 95% within 5 h, whereas the polymerization of 1a without thiophenols did not proceed under the same conditions. The promotion effect of the thiophenols on curing of bisphenol‐A type N‐phenyl benzoxazine 1b was also investigated. In the differential scanning calorimetric (DSC) analysis of the polymerization of 1b at 150 °C without using any promoters, an exothermic peak attributable to the ring‐opening reaction of benzoxazine was observed after 8 h. In contrast, in the DSC analysis of the polymerization of 1b with addition 20 mol % of p‐nitrothiophenol, an exothermic peak was observed within 2 h, to clarify the significant promoting effect of p‐nitrothiophenol. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2523–2527     

Imidazolium‐based poly(ionic liquid)s with poly(ethylene oxide) main chains: Effects of spacer and tail structures on ionic conductivity

Ten types of cationic glycidyl triazole polymers (GTPs) are prepared from combinations of five alkyl‐imidazolium units (methyl‐, ethyl‐, n‐propyl‐, iso‐propyl‐, and n‐butyl‐imidazoliums) and two spacers [di‐ and tri(ethylene glycol)s]. Since these poly(ionic liquid)s are prepared from the same sample of glycidyl azide polymer by postfunctionalization method, they have the same degree of polymerization. Therefore, the structure–property relationship can be discussed without influence of molecular weight difference. The samples are characterized by NMR, differential scanning calorimetry, and thermogravimetric analysis. The ionic conductivity data are obtained by impedance measurements. The GTPs with the tri(ethylene glycol) spacer and ethyl‐ and n‐butyl‐imidazolium units afford the highest anhydrous conductivity of 1.5 × 10^?5 S cm^?1 at 30 °C. Based on electrode polarization (EP) analysis, we calculate the conducting ion (carrier) concentration and mobility. We discuss the effect of the spacer and N‐alkyl tail structures on the ionic conductivity using the data obtained by EP analysis and X‐ray diffraction. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2896–2906     

Synthesis and characterization of photosensitive liquid crystalline poly(benzylidene‐ether)s with alkanones and methylene spacers in the main chain

Photosensitive main chain liquid crystalline poly (benzylidene‐ether)s were synthesized by Claisen‐Schmidt polycondensation reaction of 4,4′‐Diformyl‐α,ω‐diphenoxyalkanes with acetone, cyclopentanone and cyclohexanone. The diformyl precursors were synthesized from 4‐hydroxybenzaldehyde and dibromoalkanes of varying spacer lengths. The structure of the monomers and polymers was confirmed by ELEM ANAL , Fourier transform infrared, ¹H NMR and ¹³C NMR spectral analyses. Molecular weight of the polymers was determined by gel permeation chromatography and was found to be moderate. The thermogravimetric analysis data revealed that the polymers were stable up to 280 °C and start degrading thereafter. Cyclopentanone containing polymers are more stable than acetone and cyclohexanone containing polymers. The self‐extinguishing properties of the synthesized polymers were studied by the determination of the limiting oxygen index values with Van Krevelen's equation. The influence of the length of methylene spacer on phase transition was investigated with differential scanning calorimetry and proved that the isotropic temperature decreases as the spacer length increases. Polarized optical microscopic study showed that cyclohexanone containing polymer IIIb exhibit nematic schlieren texture. Crystallinity of the polymers was studied with X‐ray diffractograms. The photolysis of liquid crystalline poly(benzylidene‐ether)s revealed that the entgegen, zusammen (EZ) photoisomerization proceeds in the system. Fluorescence spectra showed violet and green emission maxima. The band gap energy is calculated from absorption spectra are in the range of 3.17–3.40 eV. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Efficient Cu(I) acetate‐catalyzed cycloaddition of multifunctional alkynes and azides: From solution to bulk polymerization

“Click” chemistry is an effective and commonly used technique in polymer chemistry for the synthesis and modification of polymers. In this study, the bulk polymerization of multifunctional alkynes and azides was achieved by the copper(I)‐catalyzed alkyne–azide 1,3‐dipolar cycloaddition. The influence of different catalyst systems on the polymerization kinetics of the “click”reaction were evaluated by differential scanning calorimetry. Surprisingly, Cu(I) acetate showed the most efficient catalytic behavior among the applied Cu(I) salts. The polymerization kinetics in solution were investigated by 1H NMR spectroscopy and size exclusion chromatography. According to the 1H NMR investigation the copper(I)‐catalyzed cycloaddition follows a second‐order kinetics with external catalysis. Additionally, the mechanical properties of the resulting polymers were investigated by depth sensing indentation. Thereby the polymerizations of the alkyne tripropargylamine with the azides 1,3‐bis(azidomethyl)benzene and 1,4‐bis(azidomethyl)benzene resulted in mechanical hard materials. Furthermore, the combination of the alkynes tripropargylamine and di(prop‐2‐yn‐1‐yl) isophorone dicarbamate and polymerization with 1,2‐bis(2‐azidoethoxy)ethane resulted in high indentation moduli. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 239–247     

Synthesis of main‐chain poly(carbazole)s via CuAAC

The synthesis and characterization of a novel family of main‐chain carbazole‐containing polymers using copper‐catalyzed azide‐alkyne cycloaddition chemistry is reported. The reactions were performed under mild conditions using readily available copper catalysts and ligands, which afforded polymeric products with M_ws up to 18 kDa. Using a range of techniques, the polymers were found to exhibit a glass transition temperature (T_g) of 85 °C, high thermal stability (T_d = 274 °C), and high photoluminescent quantum efficiency (?_f = 0.29; λ_em = 448 nm), which underscore their potential for use in organic light‐emitting diodes or other emissive devices, particularly where efficient blue emission is of value. The approach described offers practical advantages over other synthetic methods used to prepare main‐chain carbazole‐containing polymers, especially with regard to the lack of need for rigorously inert conditions and the absence of byproducts generated during the polymerization reaction. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Hemocompatibility of poly(acrylonitrile-co-N-vinyl-2-pyrrolidone)s: swelling behavior and water states

Hemocompatibility is an essential aspect of blood contacting polymers. Knowledge of the relationship between polymer structure and hemocompatibility is important in designing such polymers. In this work, the effect of swelling behavior and states of water on the hemocompatibility of poly(acrylonitrile-co-N-vinyl-2-pyrrolidone) (PANCNVP) films was studied. Platelet adhesion and plasma recalcification time tests were used to evaluate the hemocompatibility of the films. Considering the importance of surface properties on the hemocompatibility of polymers, static water contact angles were measured by both sessile drop and captive bubble methods. It was found that, on the film surface of PANCNVP with a higher NVP content, adhered platelets were remarkably suppressed and the recalcification time was longer. The total water content adsorbed on the PANCNVP film was determined through swelling experiments performed at temperatures of interest. Differential scanning calorimetry and thermogravimetric analysis were used to probe the states of water in the films. Based on the results from these experiments, it was hypothesized that the better hemocompatibility of PANCNVP films with higher NVP contents was due to their higher free water content, because water molecule exchange at the polymer/liquid interface, facilitated by a high free water content, is unfavorable for the formation of surface bound water, which causes poor hemocompatibility. [diagram in text].     

Main‐chain chiral poly(2‐oxazoline)s: Influence of alkyl side‐chain on secondary structure formation in solution

The synthesis and microwave‐assisted polymerization of a series of chiral 2‐oxazolines with varying alkyl pendant groups, namely R‐2‐ethyl‐4‐ethyl‐2‐oxazoline (R‐EtEtOx), R‐2‐butyl‐4‐ethyl‐2‐oxazoline (R‐BuEtOx), R‐2‐octyl‐4‐ethyl‐2‐oxazoline, 2‐nonyl‐4‐ethyl‐2‐oxazoline, and R‐2‐undecyl‐4‐ethyl‐2‐oxazoline (R‐UndeEtOx), are reported. A kinetic investigation of the polymerization of R‐EtEtOx revealed a living polymerization mechanism. The poly(2‐oxazoline)s containing an ethyl, butyl, and octyl pendant group form similar chiral structures according to circular dichroism measurements. When the pendant group is further elongated, the chiral structure becomes more flexible in trifluoroethanol and the thermal response in hexafluoroisopropanol (HFIP) significantly changes. The short‐range structure of poly‐R‐BuEtOx dissolved in HFIP is thermoresponsive in a complex way, due to HFIP hydrogen bonding to the polymeric amide groups, whereas the long‐range structure determined from small angle neutron scattering is insensitive to temperature demonstrating that only the local secondary structure changes with temperature. In addition, the chiral structure of poly‐R‐UndeEtOx depends on the polarity of the solvent. The short‐range structure becomes more flexible in polar solvents, most likely due to interactions with the amide groups disturbing the secondary structure. In contrast, the long‐range structural transition from an ellipsoid in the apolar n‐hexane to a rod structure in the polar n‐butanol is ascribed to better solvation of the long aliphatic side chains. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011