Polyaniline doped by a new class of dopants,benzoic acid and substituted benzoic acid: synthesis and characterization

This work reports on a new class of dopants, benzoic acid and substituted benzoic acids such as 2‐hydroxybenzoic acid, 2‐chlorobenzoic acid, 4‐nitrobenzoic acid, 2‐methoxybenzoic acid, 3‐methylbenzoic acid, 4‐methylbenzoic acid, 3‐aminobenzoic acid and 4‐aminobenzoic acid, for polyaniline. Benzoic acids can be used to dope polyaniline by mixing benzoic acid (or a substituted benzoic acid) with polyaniline in the common solvent 1‐methyl‐2‐pyrrolidone. Properties of benzoic acid doped polyaniline salts are studied using Fourier transform infra‐red, X‐ray diffraction spectroscopy, scanning electron microscopy, thermogravimetric analysis and conductivity measurements. The conductivity of polyaniline‐benzoic acid salt was found to be high (10⁻² S/cm) when compared to polyaniline‐substituted benzoic acid salts (10⁻³–10⁻⁵ S/cm). Copyright © 2005 John Wiley & Sons, Ltd.     

Study on the evaluation of mechanical and thermal properties of natural sisal fiber/general polymer composites reinforced with nanoclay

Composite materials, made by replacing traditional materials, are used because of their capability to produce tailor-made, desirable properties such as high tensile strength, low thermal expansion, and high strength to weight ratio. The need for the development of new materials is essential and growing day by day. The natural sisal/general polymer (GP) reinforced with nanoclay composites has become more attractive due to its high specific strength, light weight, and biodegradability. In this study, sisal–nanoclay composite is developed and its mechanical properties such as tensile strength, flexural strength, and impact strength are evaluated. The interfacial properties, internal cracks, and internal structure of the fractured surface are evaluated using scanning electron microscope. The thermal disintegration of composites are evaluated by thermogravimetric analysis. The results indicate that the incorporation of nanoclay in sisal fiber/GP can improve its properties and can be used as a substitute material for glass fiber-reinforced polymer composites.     

Physicochemical characterization of α‐chitin, β‐chitin,and γ‐chitin separated from natural resources

We isolated α‐chitin, β‐chitin, and γ‐chitin from natural resources by a chemical method to investigate the crystalline structure of chitin. Its characteristics were identified with Fourier transform infrared (FTIR) and solid‐state cross‐polarization/magic‐angle‐spinning (CP–MAS) ¹³C NMR spectrophotometers. The average molecular weights of α‐chitin, β‐chitin, and γ‐chitin, calculated with the relative viscosity, were about 701, 612, and 524 kDa, respectively. In the FTIR spectra, α‐chitin, β‐chitin, and γ‐chitin showed a doublet, a singlet, and a semidoublet at the amide I band, respectively. The solid‐state CP–MAS ¹³C NMR spectra revealed that α‐chitin was sharply resolved around 73 and 75 ppm and that β‐chitin had a singlet around 74 ppm. For γ‐chitin, two signals appeared around 73 and 75 ppm. From the X‐ray diffraction results, α‐chitin was observed to have four crystalline reflections at 9.6, 19.6, 21.1, and 23.7 by the crystalline structure. Also, β‐chitin was observed to have two crystalline reflections at 9.1 and 20.3 by the crystalline structure. γ‐Chitin, having an antiparallel and parallel structure, was similar in its X‐ray diffraction patterns to α‐chitin. The exothermic peaks of α‐chitin, β‐chitin, and γ‐chitin appeared at 330, 230, and 310, respectively. The thermal decomposition activation energies of α‐chitin, β‐chitin, and γ‐chitin, calculated by thermogravimetric analysis, were 60.56, 58.16, and 59.26 kJ mol^?1, respectively. With the Arrhenius law, ln β was plotted against the reciprocal of the maximum decomposition temperature as a straight line; there was a large slope for large activation energies and a small slope for small activation energies. α‐Chitin with high activation energies was very temperature‐sensitive; β‐Chitin with low activation energies was relatively temperature‐insensitive. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3423–3432, 2004     

Surface modification of glass beads with poly(acrylic acid)

Non‐porous P₂ glass beads were etched with sodium hydroxide to increase the number of silanol groups that could be used to modify the surface. The etched glass beads were then functionalized with 3‐aminopropyltriethoxysilane (APS) and/or glycidoxypropyltrimethoxysilane (GPS). The surface of the glass beads were further modified with poly(acrylic acid) (PAA) by reacting the carboxyl groups on PAA with the amino groups of the pregrafted APS. The chemical modifications were characterized by FT‐IR spectroscopy, particle size analyzer and tensiometry for contact angle and porosity measurements. Five different molecular weight PAA polymers ranging from 2000 to 3,000,000 were grafted with less than expected increase of grafted PAA with molecular weight. The amount of APS and PAA on the surface was determined from thermogravimetric analysis and elemental analysis data. The surface properties of the surface modified glass beads were determined by measuring water and hexane penetration rate and contact angle. The surface morphology was examined by scanning electron microscopy. Copyright © 2006 John Wiley & Sons, Ltd.     

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     

Fabrication and properties of poly(propylene carbonate)/calcium carbonate composites

Composites of poly(propylene carbonate) (PPC) reinforced with micrometric and nanometric calcium carbonate particles were prepared via melt mixing followed by compression molding. The morphology and mechanical and thermal behaviors of the composites were investigated. Static tensile tests showed that the tensile strength, stiffness, and ductility of the composites tended to increase with increasing contents of micrometric calcium carbonate particles. This improvement in the tensile properties was attributed to good interfacial adhesion between the fillers and matrix, as evidenced by scanning electron microscopy examination. However, because of the agglomeration of calcium carbonate nanoparticles during blending, those composites with nanoparticles exhibited the lowest tensile strength. Thermogravimetric measurements revealed that the incorporation of calcium carbonate into PPC resulted in a slight improvement in its thermooxidative stability. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1806–1813, 2003     

Partially pyrolyzed poly(dimethylsiloxane)‐based networks: Thermal characterization and evaluation of the gas permeability

In this investigation, the preparation and characterization of partially pyrolyzed membranes based on poly(dimethylsiloxane) (PDMS) are described. These membranes were obtained by the crosslinking of silanol‐terminated PDMS with multifunctional nanoclusters derived from the reaction of pentaerythritoltriacrylate with 2‐aminoethyl‐3‐aminopropyltrimethoxysilane and the in situ polycondensation of tetraethylortosilicate, followed by the thermal treatment of the resulting membranes at different temperatures. The partially pyrolyzed membranes were characterized with infrared spectroscopy, thermogravimetry, elemental analyses, dynamic mechanical analysis, small‐angle X‐ray scattering, and scanning electron microscopy. The membranes exhibited improvements in the thermal stability and mechanical strength. Even with distinct compositions with respect to the Si/O and Si/C ratios, the flexibility of these materials was maintained. The flux rates of the gases through the membranes were measured for N₂, H₂, O₂, CH₄, and CO₂, at 25 °C. The permeability of the membranes changed with increases in the pyrolysis and oxidation temperatures. These membranes could be described as PDMS chains separated by inorganic clusters. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 299–309, 2007.     

Poly(n‐alkylsilsesquioxane)s: Synthesis,characterization, and modification with poly(dimethylsiloxane)

Self‐supported translucent films constituted of poly(n‐octylsilsesquioxane) or poly(n‐dodecylsilsesquioxane) were obtained from the hydrolysis and condensation of n‐octyltriethoxysilane (OTES) or n‐dodecyltriethoxysilane (DTES), respectively. Dense films were obtained in the absence of organic solvents, with dibutyltin diacetate as catalyst. These films exhibited good optical transparency and thermal stability. The incorporation of oligomeric dimethylsiloxane units (D^Me,Me) in these materials, derived from silanol‐terminated poly(dimethylsiloxane) (PDMS) or 1,1,3,3‐tetramethyl‐1,3‐diethoxydisiloxane (TMDES), was carried out during the hydrolysis and condensation of OTES and DTES and was confirmed by solid‐state ²⁹Si NMR. Poly(n‐octylsilsesquioxane) showed a glass‐transition temperature at ?65 °C, due to the increase in the free volume, promoted by the bulky n‐octyl groups. The differential scanning calorimetric (DSC) curves of the polymer derived from DTES were characterized by first‐order transitions at temperatures ranging from ?15.8 to ?0.7 °C. Further studies of these networks by low‐temperature XRD evidenced narrowing of the diffraction halos suggesting a partial order–disorder transition for these materials at lower temperatures. Good thermal stability up to 350 °C and the solvent‐free production process make these polymers potential candidates for the development of self‐supported hydrophobic protective coatings. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1220–1229, 2010     

Mechanical properties of phenol/formaldehyde resin composites reinforced by cellulose microcrystal with different aspect ratio extracted from sisal fiber

Sisal cellulose fiber (SCF) and sisal fiber cellulose microcrystal (SFCM), produced with sulfate pulping method and ball‐milling approach separately, were in‐situ polymerized and dispersed into phenol/formaldehyde (PF) resin, to manufacture SCF/PF and SFCM/PF composites via rolling and molding method and investigate the effect of SCF and SFCM on the impact, flexural, and dynamic mechanical properties of the SCF/PF and SFCM/PF composites. As a result, under the condition of same content, SFCM could preferably enhance these properties maybe resulting from the better dispersion in resin matrix than SCF. In particular, when SFCM content was 7%, the impact strength and equilibrium relaxation modulus of the SFCM/PF composite were increased by 26.5% and 37.7%, while the creep deformation was decreased by 26.5%. In addition, when SFCM content was 5%, the flexural strength, initial storage modulus and glass transition temperature of SFCM/PF composite were increased by 8.5%, 22.6%, and 13°C. Copyright © 2016 John Wiley & Sons, Ltd.     

A new study on effect of various chemical treatments on Agave Americana fiber for composite reinforcement: Physico-chemical,thermal, mechanical and morphological properties

This research is focused to fundamentally understand the benefits of using Agave Americana C. plant as potential reinforcement in polymeric composites. The fibers were extracted from the external part of the bark of the plant, which grows worldwide in pastures, grasslands, open woodlands, coastal and riparian zones. In order to use the natural fiber as reinforcement it is paramount important to probe their chemical composition, microstructural behavior and mechanical properties. Hence, firstly the extracted fibers were chemically treated with NaOH, stearic acid, benzoyl peroxide and potassium permanganate. The chemical composition in terms of cellulose, hemicellulose, lignin and other waxy substances were determined using a standard TAPPI method. FT-IR technique was used to understand the character of molecular bonds, crystallinity and their correlations with various bonds in fiber structure. The thermal stability was investigated through thermogravimetric and differential scanning calorimetric analysis, and the mechanical characterization was performed by applying standard tensile test. The surface morphology of fibers was examined through scanning electron microscopy (SEM) and finally reliability scrutiny of all the analysis was carried out. The results of chemical modification techniques applied on the surfaces of natural fibers allows to produce superior fibers used to form the novel composite materials for light-weight application.     

Synthesis,morphology, and viscoelastic properties of cyanate ester/polyhedral oligomeric silsesquioxane nanocomposites

Cyanate ester (PT‐15, Lonza Corp) composites containing the inorganic–organic hybrid polyhedral oligomeric silsesquioxane (POSS) octaaminophenyl(T₈)POSS [ 1 ; (C₆H₄NH₂)₈(SiO_1.5)₈] were synthesized. These PT‐15/POSS‐ 1 composites (99/1, 97/3, and 95/5 w/w) were characterized by X‐ray diffraction (XRD), transmission election microscopy (TEM), dynamic mechanical thermal analysis, solvent extraction, and Fourier transform infrared. The glass‐transition temperatures (T_g's) of the composite with 1 wt % 1 increased sharply versus the neat PT‐15, but 3 and 5 wt % 1 in these cyanate ester composites depressed T_g. All the PT‐15/POSS composites exhibited higher storage modulus (E′) values (temperature > T_g) than the parent resin, but these values decreased from 1 to 5 wt % POSS. The loss factor peak intensities decreased and their widths broadened upon the incorporation of POSS. XRD, TEM, and IR data were all consistent with the molecular dispersion of 1 due to the chemical bonding of the octaamino POSS‐ 1 macromer into the continuous cyanate ester network phase. The amino groups of 1 reacted with cyanate ester functions at lower temperatures than those at which cyanate ester curing by cyclotrimerization occurred. In contrast to 1 , 3‐cyanopropylheptacyclopentyl(T₈)POSS [ 2 ; (C₅H₉)₇(SiO_1.5)₈CH₂CH₂CH₂CN] had low solubility in PT‐15 and did not react with the resin below or at the cure temperature. Thus, phase‐separated aggregates of 2 were found in samples containing 1–10 wt % 2 . Nevertheless, the T_g and E′ values (temperature > 285 °C) of these composites increased regularly with an increase in 2 . © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3887–3898, 2005     

Thermochemically induced binding of methyl orange to polycations containing primary amine groups

The thermochemical transformation of electrostatically formed complexes of methyl orange (MO) with polycations containing primary amine groups such as ammonium salts afforded new polymers with a high concentration of covalently bound 4‐N,N‐dimethylaminoazobenzene groups in the side chain. Poly(allylamine hydrochloride) and poly(β‐aminoethylene acrylamide hydrochloride) were employed as support polycations for MO. The transformation of sulfonate–ammonium ion pairs into sulfonamide bonds, via heating at an elevated temperature, was supported by the polymer properties before and after the thermal treatment. The polymer structure changes were monitored with elemental analysis, Fourier transform infrared, ¹H NMR, and ultraviolet–visible absorption spectroscopy, and thermogravimetric analysis. The spacer length between the backbone and azobenzene structures used as side chains strongly influenced the polymer properties before and after the heat‐induced reaction. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5898–5908, 2006     

Ionic networks derived from the protonation of dendritic amines with carboxylic acid end‐functionalized PEGs

The synthesis and characterization of novel ionic networks linked by the ammonium salts of poly(propylene imine) (PPI) dendrimers of the first (PPI G1) and second (PPI G2) generation and two short bis carboxymethyl ether terminated poly(ethylene glycol)s (DiCOOH‐PEG) with different molecular weights (M_n ～ 250 and M_n ～ 600) are reported. Likewise, an ionic network based on PPI G1 and a long αω‐dicarboxylic acid functionalized PEG (M_n ～ 4800) were evaluated. Simpler ionic structures based on tris(2‐aminoethyl)amine or hexamethylene diamine and the short DiCOOH‐PEGs are also investigated. The ionic structures formed were confirmed by differential scanning calorimetry, Fourier Transform Infrared spectroscopy in the attenuated‐total‐reflection mode, and ¹H‐¹³C NMR spectroscopy. A comprehensive ¹H NMR analysis revealed that only the primary amines of the PPI G1 dendrimer residing at the periphery take part in the ionic network formation. In the case of PPI G2, the picture is less clear. A thorough investigation of the thermal degradation of the utilized precursors and all the ionic materials prepared was additionally performed by thermogravimetric analysis. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthetic fabrics coated with zinc oxide nanoparticles by electroless deposition: Structural characterization and wetting properties

Electroless deposition was successfully applied in developing crystalline particles of zinc oxide onto polyester textile materials; this deposition is here presented in comparison with other materials made from poly(lactic acid), polyamide or hemp. Structural and spectroscopic characterization of the raw and deposited samples has been performed. The structure of zinc oxide particles was that of wurtzite type as indicated by X‐ray diffraction (XRD) and scanning electron microscopy (SEM). Crystallites were 20–500 nm in diameter and up to 1 µm in length. The grown particles cover the fibers not only on the fabric surface but in the textile depth. Contact angle measurement by the sessile drop method was used to study the wettability behavior of the investigated composite systems. The hierarchical roughness structure generates superhydrophobic properties onto polyester fabrics, for which water contact angles exceed 150°. The other functionalized samples also become more hydrophobic after deposition. Cassie‐Baxter model was found suitable to describe the behavior, though the fraction of surface occupied by the water–solid interface is high enough. The electroless deposition technique applied previously for cotton fabrics was once more proven to be highly reproducible, easy scalable, and cheap, allowing a wide range of applications. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1427–1437     

Synthesis and characteristics of novel chelate fiber containing amine and amidine groups

A polyacrylonitrile (PAN) fiber was adopted for the backbone of a chelate polymer and poly(acrylo‐amidino ethylene amine) (PAEA) was prepared through a one‐step reaction between the PAN fiber and ethylenediamine (EDA). The maximum removal capacity and degree of substitution were 7.8 meq per gram of dried PAEA and 98%, respectively. The PAEA was tested as an adsorbent in single and two‐component metal aqueous solutions under changing pH. The Cu²⁺ ion accomplished maximum adsorption amount at pH 3 and the order of maximum adsorbed amounts on PAEA is Cu²⁺ > Ag⁺ > Zn²⁺ > Ni²⁺ > Pb²⁺ in molar basis. FT‐IR spectroscopy was employed to characterize the chemical bonding in metal aqueous solutions and surface morphology was examined using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Copyright © 2004 John Wiley & Sons, Ltd.     

New polysaccharide-g-polyacrylonitrile copolymers: synthesis and thermal characterization

Various natural and modified polysaccharides (i.e. arabic gum, tragacanth gum, xanthan gum, sodium alginate, chitosan, sodium carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose) were modified using ceric-initiated graft polymerization of acrylonitrile under inert atmosphere. Grafting was confirmed using spectral (FT-IR) proofs. The grafting parameters were determined by conventional methods. Thermal characteristics of the homopolymer-free copolymers were studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) under nitrogen atmosphere. The major thermal transitions as well as the activation energy of the major decomposition stages were investigated. The polyacrylonitrile (PAN)-grafted polysaccharides were recognized to be thermally stable more than the corresponding non-grafted substrates, although they begin to decompose at relatively lower temperatures than the non-grafted counterparts. Copyright © 2003 John Wiley & Sons, Ltd.     

Preparation and characterization of nano‐platelet‐like hydroxyapatite/gelatin nanocomposites

Nature has succeeded in creating numerous bionanocomposites such as bones and teeth consisting of nano‐platelets and biopolymers. Understanding of the mechanisms of formation and of the relation between structure and properties is vital for development of new materials for biomedical and engineering applications. In this work, varying contents of nano‐platelet‐like hydroxyapatite (HAp) has been used to reinforce gelatin (Gel) to produce nanocomposites. The prepared HAp/Gel nanocomposites were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric (TG/DTG) analyses. XRD, TEM, and FTIR results confirm the synthesis of intercalated and exfoliated nanostructures depending on the amount of gelatin. TG results reveal that the intercalated HAp/gelatin nanocomposites show improved thermal properties as compared to pristine gelatin. The results reported here can be expanded to other HAp–polymer systems, thus paving a new way of designing and fabricating biomemitic nanocomposites for future engineering and particularly for biomedical applications. Copyright © 2010 John Wiley & Sons, Ltd.     

Equilibrium adsorption model of anions onto a novel synthesized chelating fiber under various pHs and Fourier transform infrared study of these adsorptions

In this article, we present a new adsorption model of anion particles onto a chelating fiber. Nonideal H⁺ adsorption on the chelating fiber can be described adequately by the use of the heterogeneity factor β and the parameter Φ indicates the geometric factor of effective concentration in this model. The best fits of amines adsorption data were obtained by means of the developed model using two factors. Poly(acrylo‐amidino diethylene diamine) was synthesized as a chelating polymer through the coupling of diethylene triamine with polyacrylonitrile fiber in the presence of AlCl₃ · 6H₂O addition. Chromate ion and phosphate ion adsorption data on the synthesized poly(acrylo‐amidino diethylene diamine) were obtained. Fourier transform infrared studies of these adsorptions were also performed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2430–2440, 2004     

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     

Synthesis and characterization of high nitrile content polyimides as dielectric films for electrical energy storage

Three new isomeric diamines containing three, oxy‐linked benzonitriles (3BCN), one of which is asymmetric (meta, para, or m, p), are synthesized in a 3‐step sequence. Polycondensation of these diamines and four common dianhydrides (6FDA, OPDA, BTDA, and PMDA) in N,N‐dimethylacetamide via poly(amic acid) precursors and thermal curing at temperatures up to 300 °C lead to three series of tough, creasable polyimide (PI) films (tensile moduli = 1.63 ? 2.86 GPa). Among these PIs, two PMDA‐based PIs possess relatively high crystallinity and two OPDA‐based PIs, low crystallinity, whereas all 6FDA‐ and BTDA‐based PIs, and m,m‐3BCN‐OPDA‐PI are amorphous, readily soluble in common polar aprotic solvents. Thermally stable and having high T_g (216 ? 341 °C), these PIs lose 5% weight around 493–503 °C in air and 463–492 °C in nitrogen. Dielectric properties have been evaluated by broadband dielectric spectroscopy (BDS) and electric displacement‐electric‐field (D‐E) loop measurements. D‐E loop results show an increase in high temperature permittivity (at 190 °C/1 kHz) from 2.9 (for parent PI CP2 with no nitrile group) to as high as 4.9 for these PIs, while keeping their dielectric loss relatively low. Thus, an increase in dipole moment density by the presence of three neighboring CN per repeat unit can increase the overall permittivity, which could be further enhanced by sub‐T_g mobility of para‐phenylene linkages (BDS results). Published 2014. J. Polym. Sci., Part A: Polym. Chem. 2014 J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 422–436