Significant glass‐transition‐temperature increase through hydrogen‐bonded copolymers

The role of hydrogen bonding in promoting intermolecular cohesion and higher glass‐transition temperatures of polymer is a subject of longstanding interest. A series of poly(vinylphenol‐co‐vinylpyrrolidone) copolymers were prepared by the free‐radical copolymerization of acetoxystyrene and vinylpyrrolidone; this was followed by the selective removal of the acetyl protective group, with corresponding and significant glass‐transition‐temperature increases after this procedure. The incorporation of acetoxystyrene into poly(vinylpyrrolidone) resulted in lower glass‐transition temperatures because of the reduced dipole interactions in its homopolymers. However, the deacetylation of acetoxystyrene to transform the poly(vinylphenol‐co‐vinylpyrrolidone) copolymer enhanced the higher glass‐transition temperature because of the strong hydrogen bonding in the copolymer chain. The thermal properties and hydrogen bonding of these two copolymers were investigated with differential scanning calorimetry and Fourier transform infrared spectroscopy, and good correlations between the thermal behaviors and IR results were observed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2313–2323, 2002     

Partially renewable copolyesters prepared from acetalized d‐glucitol by solid‐state modification of poly(butylene terephthalate)

The backbone of poly(butylene terephthalate) (PBT) was modified with 2,4:3,5‐di‐O‐methylene‐D ‐glucitol (Glux) using solid‐state modification (SSM). The obtained copolyesters proved to have a non‐random overall chemical microstructure. The thermal properties of these semicrystalline, block‐like, Glux‐based materials were extraordinary, showing higher melting points, and glass transition temperatures compared with other sugar‐based copolyesters prepared by SSM. These remarkable thermal properties were a direct result of the inherently rigid structure of Glux and the relatively slow randomization of the block‐like chemical microstructure of the Glux‐based copolyesters in the melt. SSM proved to be a versatile tool for preparing partially biobased copolyesters with superior thermal properties. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 164–177     

Molecular dynamics simulation study of glass transition in hydrated Nafion

The thermal transition of Nafion is studied using a molecular dynamics simulation through a chemically realistic model. Static and dynamic properties of polymer melts with different water contents are investigated over a wide range of temperatures to obtain viscometric and calorimetric glass transition temperatures. The effect of cooling rate of the simulation on the glass transition of the hydrated polymer is also examined within the well‐known Williams–Landel–Ferry (WLF) equation. Variation of relaxation times versus temperature shows a fragile‐to‐strong transition. The hydration level has a significant impact on the static and dynamic properties of the polymer chains and water molecules confined in nanometric spaces between polymer chains. The results of this study are useful to predict the behavior of Nafion for various applications including fuel cells, sensors, actuators, and shape memory devices at different temperatures. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 907–915     

Synthesis and cationic photopolymerization of new fluorinated,polyfunctional propenyl ether oligomers

New fluorinated, polyfunctional propenyl ether functionalized resins were synthesized, and their behavior in cationic photopolymerization was investigated. The photopolymerization proceeded efficiently with a high double‐bond conversion (>90%), giving rise to UV‐cured coatings characterized by low glass‐transition temperatures (?33 °C ≤ glass‐transition temperature ≤ ?15 °C) and hydrophobic surface properties. A fluorinated additive was also employed as a reactive additive in the cationic photopolymerization of trimethylolpropane tripropenyl ether, increasing the double‐bond conversion, polymer network flexibility, thermal stability, and surface hydrophobicity. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6943–6951, 2006     

Parameterization of electrostatic interactions for molecular dynamics simulations of heterocyclic polymers

The paper focuses on the problem of electrostatic interactions in molecular dynamics simulations of thermal properties of heterocyclic polymers. The study focuses on three thermoplastic polyimides synthesized on the basis of 1,3‐bis‐(3′,4‐dicarboxyphenoxy)benzene (dianhydride R) and three diamines: 4,4′‐bis‐(4″‐aminophenoxy) diphenylsulfone (diamine BAPS), 4,4′‐bis‐(4″‐aminophenoxy) biphenyl (diamine BAPB), and 4,4′‐bis‐(4''‐aminophenoxy) diphenyloxide (diamine BAPO). In the molecular dynamics simulations these polyimides were described by the Gromos53a5 force field. To parameterize the electrostatic interactions four methods of calculating the partial atomic charges were chosen: B3LYP/6–31G*(Mulliken), AM1(Mulliken), HF/6–31G*(Mulliken), and HF/6–31G*(ChelpG). As our parameterization is targeted to reproduce thermal properties of the thermoplastic polyimides, the choice of proper partial charges was finalized on a basis of the closest match between computational and experimental data for the thermal expansion coefficients of the polyimides below glass transition temperatures. Our finding clearly show that the best agreement with experimental data is achieved with the Mulliken partial atomic charges calculated by the Hartree‐Fock method with 6–31G* basis set. Furthermore, in addition to the thermal expansion coefficients this set of partial atomic charges predicts an experimentally observed relationship between glass transition temperatures of the three polyimides under study: . A mechanism behind the change in thermal properties upon the change in the chemical structure in considered polyimides may be related to an additional spatial ordering of sulfone groups due to dipole‐dipole interactions. Overall, the modified force‐field is proved to be suitable for accurate prediction of thermal properties of thermoplastic polyimides and can serve as a basis for building up atomistic theoretical models for describing other heterocyclic polymers in bulk. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 912–923     

Synthesis and nonlinear optical properties of novel Y‐type polyester containing tricyanovinylthiazolylazoresorcinoxy group with enhanced thermal stability of dipole alignment

Novel Y‐type polyester 4 containing 5‐methyl‐4‐{5‐(1,2,2‐tricyanovinyl)‐2‐thiazolylazo}resorcinoxy groups as nonlinear optical (NLO) chromophores, which are parts of the polymer backbone, was prepared, and its NLO properties were investigated. Polyester 4 is soluble in common organic solvents such as N,N‐dimethylformamide and dimethylsulfoxide. Polymer 4 shows a thermal stability up to 250 °C from thermogravimetric analysis with glass‐transition temperature obtained from differential scanning calorimetry of approximately 94 °C. The second harmonic generation (SHG) coefficient (d₃₃) of poled polymer film at 1560‐nm fundamental wavelength is 8.12 × 10^?9 esu. The dipole alignment exhibits a thermal stability even at 6 °C higher than glass‐transition temperature (T_g), and no significant SHG decay is observed below 100 °C due to the partial main‐chain character of polymer structure, which is acceptable for NLO device applications. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

High performance thermosets from a curable Diels–Alder polymer possessing benzoxazine groups in the main chain

A high‐molecular‐weight polymer (PBz) possessing reactive benzoxazine groups in the main chain was prepared through the Diels–Alder reaction using bis(3‐furfuryl‐3,4‐dihydro‐2H‐1,3‐benzoxazinyl)isopropane (BPA‐FBz) and bismaleimide (BMI) as monomers. The chemical structure of PBz is characterized with FTIR and ¹H NMR. The polymer PBz was further thermally reacted with a high performance polymer (PBz‐R) through the ring‐opening addition reaction of benzoxazine groups and the addition reaction of maleimide groups. PBz‐R exhibit a high glass transition temperature of 242 °C, good thermal stability, high flame retardancy, high mechanical strength, and great flexibility. Another crosslinked polymer (PBz‐BR) curing from the mixture of BPA‐FBz and BMI was also prepared. The properties of PBz‐BR are also attractive but, however, not as good as what observed with PBz‐R. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6509–6517, 2008     

Synthesis of new thermosetting poly(2,6‐dimethyl‐1,4‐phenylene oxide)s containing epoxide pendant groups

A new class of thermosetting poly(2,6‐dimethyl‐1,4‐phenylene oxide)s containing pendant epoxide groups were synthesized and characterized. These new epoxy polymers were prepared through the bromination of poly(2,6‐dimethyl‐1,4‐phenylene oxide) in halogenated aromatic hydrocarbons followed by a Wittig reaction to yield vinyl‐substituted polymer derivatives. The treatment of the vinyl‐substituted polymers with m‐chloroperbenzoic acid led to the formation of epoxidized poly(2,6‐dimethyl‐1,4‐phenylene oxide) with variable pendant ratios, and the structures and properties were studied with nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and gel permeation chromatography. The ratios of pendant functional groups were tailored for the polymer properties, and the results showed that the glass‐transition temperatures increased as the benzylic protons were replaced by bromo‐, vinyl‐, or epoxide‐functional groups, whereas the thermal stability decreased in comparison with the original polymer. Within a molar fraction of 20–50%, the degree of functionalization had little effect on the glass‐transition temperature; however, it correlated inversely with the thermal stability of each functionalized polymer. The thermal curing behavior of the epoxide‐functionalized polymer was enhanced by the increment of the pendant functionality, which resulted in a significant increase in the glass‐transition temperature as well as the thermal stability after the curing reaction. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5875–5886, 2006     

Synthesis and optical properties of poly(aryl ether ketone)s incorporating porphyrins in the backbones

A series of novel soluble poly(aryl ether ketone)s (PAEKs) based on 5,10‐bis(4‐hydroxyphenyl)?15,20‐diphenylporphyrin (cis‐DHTPP), 4,4′‐(hexafluoroisopropylidene) diphenol (6FBPA) and 4,4′‐difluorobenzophenone (DFB) were synthesized and characterized by FT‐IR, ¹H‐NMR, UV–vis and fluorescence spectroscopies. The intrinsic photophysical properties of porphyrins were preserved because of the absence of photoinduced electron transfer in the polymer chains. Investigation of the copolymers thermal properties indicated that these polymers had high glass transition temperatures and excellent thermal stabilities. The results of Z‐scan and optical limiting measurements manifested that incorporation of the porphyrin chromophore into the main chain engendered the novel PAEKs with superior nonlinear optical properties and optical limiting function, which could be effectively tuned by varying the molar ratio of porphyrin monomers. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1282–1290     

Metallocene copolymers of propene and 1‐hexene: The influence of the comonomer content and thermal history on the structure and mechanical properties

The relationships between the structure and properties have been established for copolymers of propylene and 1‐hexene synthesized with an isotactic metallocene catalyst system. The most important factor affecting the structure and properties of these copolymers is the comonomer content. The thermal treatment, that is, the rate of cooling from the melt, is also important. These factors affect the thermal properties, the degree of crystallinity, and therefore the structural parameters and the viscoelastic behavior. A slow cooling from the melt favors the formation of the γ phase instead of the α modification. Regarding the viscoelastic behavior, the β relaxation, associated with the glass‐transition temperature, is shifted to lower temperatures and its intensity is increased as the 1‐hexene content raises. The microhardness values are correlated with those of the storage modulus deduced from dynamic mechanical thermal analysis curves, and good linear relations have been obtained between these parameters. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1253–1267, 2006     

Homogeneous anionic PPE hybrids with silica gel

Anionic poly(p‐phenylene‐ethynylene) (PPE) incorporated polymer hybrids were synthesized from the PPE and tetramethoxysilane together with the organic polymers such as poly(vinylpyrrolidone) via a sol–gel method. Up to 10 wt % of the anionic PPE could be dispersed homogeneously in the resulting polymer hybrid matrix. The obtained polymer hybrids exhibited controllable photoluminescence properties by the modification of the internal environment of organic–inorganic polymer hybrids by changing the organic/inorganic ratios. The photoluminescence of the anionic PPE surrounded by the polymer hybrid matrix was reinforced against the thermal irradiation. Moreover, the photoluminescence of the obtained organic–inorganic polymer hybrids was also tuned by utilizing ionic interactions between the anionic PPE and the inorganic matrix. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3749–3755, 2008     

Studies on poly(ε‐caprolactone)/thiodiphenol blends: The specific interaction and the thermal and dynamic mechanical properties

The effects of several low molecular weight compounds with hydroxyl groups on the physical properties of poly(ε‐caprolactone) (PCL) were investigated by Fourier transform infrared (FTIR) spectroscopy and high‐resolution solid‐state ¹³C NMR. PCL and 4,4′‐thiodiphenol (TDP) interact through strong intermolecular hydrogen bonds and form hydrogen‐bonded networks in the blends at an appropriate TDP content. The thermal and dynamic mechanical properties of PCL/TDP blends were investigated by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis, respectively. The melting point of PCL decreased, whereas both the glass‐transition temperature and the loss tangent tan δ of the blend increased with an increase in TDP content. The addition of 40 wt % TDP changed PCL from a semicrystalline polymer in the pure state to a fully amorphous elastomer. The molecules of TDP lost their crystallizability in the blends with TDP contents not greater than 40 wt %. In addition to TDP, three other PCL blend systems with low molecular weight additives containing two hydroxyl groups, 1,4‐dihydroxybenzene, 1,4‐di‐(2‐hydroxyethoxy) benzene, and 1,6‐hexanediol, were also investigated with FTIR and DSC, and the effects of the chemical structure of the additives on the morphology and thermal properties are discussed. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1848–1859, 2000     

Synthesis and characterization of end‐group modified hyperbranched polyetherimides

End‐group modified hyperbranched polyetherimides were prepared by a one‐pot, two‐step reaction sequence. General synthetic techniques were developed to prepare both monofunctional terminating segments and the corresponding modified polyetherimide hyperbranched polymers. Monofunctional groups were used to terminate an AB₂‐type polycondensation reaction, generating capped hyperbranched polymers (HBPs). The composition and constitution of the end groups controlled the solubility and thermal properties of the HBPs. For the same polymer backbone, different end groups were able to shift the glass‐transition temperature nearly 100 °C. End‐group modification greatly influenced the film‐forming ability of the HBPs. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 936–946, 2002     

Computer simulation of the heat-resistant polyimides ULTEM™ and EXTEM™ with the use of GROMOS53a6 and AMBER99 force fields

An atomistic computer simulation was performed for the polyimides ULTEM? and EXTEM? via the molecular-dynamics method with the use of Gromos53a6 and Amber99 force fields. For parameterization of electrostatic interactions, the partial atomic charges were calculated through quantum-chemical methods. The temperature dependence of density and the thermal-expansion coefficients for the polyimides were obtained. The calculated density values of the polyimides at room temperature and their coefficients of thermal expansion in the glassy state are in agreement with available experimental data. It is shown that inclusion of electrostatic interactions is necessary for simulation of the thermophysical characteristics of the considered polyimides.     

Molecular design,synthesis, and nonlinear optical properties of novel T‐type polyimides with exceptionally high thermal stability of the second harmonic generation

2,5‐Bis‐(3,4‐dicarboxyphenylcarboxyethoxy)‐4′‐nitrostilbene dianhydride was prepared and reacted with 1,4‐phenylenediamine, 4,4′‐oxydianiline, 4,4′‐diaminobenzanilide, and 4,4′‐(hexafluoroisopropylidene)dianiline to yield unprecedented novel T‐type polyimides ( 4 – 7 ) containing 2,5‐dioxynitrostilbenyl groups as nonlinear optical chromophores, which constituted parts of the polymer backbones. 4 – 7 were soluble in polar solvents such as acetone and N,N‐dimethylformamide. They showed thermal stability up to 300 °C in thermogravimetric analysis thermograms; the glass‐transition temperatures obtained from differential scanning calorimetry thermograms were around 153 °C. The second harmonic generation (SHG) coefficients (d₃₃) of poled polymer films at the 1064‐cm^?1 fundamental wavelength were around 4.35 × 10^?9 esu. The dipole alignment exhibited exceptionally high thermal stability even at 45 °C higher than the glass‐transition temperature, and there was no SHG decay below 200 °C because of the partial main‐chain character of the polymer structure, which was acceptable for nonlinear optical device applications. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3189–3199, 2004     

Photochemical isomerization of norbornadiene‐containing polytriazoles obtained by click chemistry polyaddition

Polyesters and polyethers containing norbornadiene (NBD) and 1,2,3‐triazole units in the main chain are prepared by step growth polymerization of diester or diether NBD‐based dialkynes with different aromatic diazides using copper‐catalyzed azide–alkyne cycloaddition. The solubility and the physical properties of the resulting polytriazoles are investigated by differential scanning calorimetry, thermogravimetric analysis, size exclusion chromatography, and ¹H NMR spectroscopy, and are discussed taking into account of the chemical structures of the monomers. All of them are amorphous with glass transition temperatures ranging from 51 to 117 °C, number average molecular weight (M_n) values from 16 to 43 kDa and thermal degradation (T_d10) values from 175 to 292 °C. The photochemical valence isomerization (PVI) of the NBD units into quadricyclanes (QC) is investigated using UV–vis spectroscopy of polymer films spin‐coated onto quartz substrates. For the first time the PVI of NBD into QC is demonstrated by ¹H NMR spectroscopy. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 223–231     

Development of hydrogenated ring‐opening metathesis polymers

New hydrogenated ring‐opening metathesis polymers with excellent thermal and optical properties were developed. These polymers were prepared by the ring‐opening metathesis polymerization of ester‐substituted tetracyclododecene monomers followed by the hydrogenation of the main‐chain double bond. The degree of hydrogenation was an important factor for the thermal stability of the polymers, and as complete hydrogenation as possible was necessary to obtain a thermally stable polymer. The completely hydrogenated ring‐opening polymer derived from 8‐methyl‐8‐methoxycarbonyl‐substituted monomer has a glass‐transition temperature of 171 °C and a 5% weight‐loss temperature of 446 °C. This polymer has excellent thermal and optical properties because of its bulky and unsymmetrical polycyclic structure in the main chain and is an alternative to glass or other transparent polymers such as poly(methyl methacrylate) and polycarbonate resin. This polymer has also been used in a wide variety of applications, such as optical lenses, optical disks, optical films, and optical fiber. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4661–4668, 2000     

Noncovalent functionalization of multiwalled and double‐walled carbon nanotubes: Positive effect of the filler functionalization on high glass transition temperature epoxy resins

Double‐walled carbon nanotubes (DWCNTs) and multiwalled carbon nanotubes (MWCNTs) were modified using melamine to attach ? NH₂ to the surface of these fillers, without previous oxidation of their graphene layers. FT‐Raman, elemental (chemical) and thermogravimetric analysis, confirmed the modification, which was more extensive for DWCNTs. The potential of this modification was evaluated by adding the melamin‐modified nanotubes to thermosets based on diglycidyl ether of bisphenol A (resin) and polycyclic amine (hardener). Broadening of the glass transition interval and an increase between 7 and 8 °C of the glass transition temperatures show better filler/matrix interaction for the nanocomposites based on melamine‐modified nanotubes. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1860–1868, 2009     

Sorption of n‐hexane in amorphous polystyrene

Sorption properties of pure n‐hexane vapor in amorphous polystyrene (PS) were studied at 298 K by thermogravimetry under controlled vapor pressure. Two sorption–desorption cycles were performed by varying the relative pressure between 0 and 0.91. Mixing of PS with n‐hexane resulted in a strong plasticization, which was evidenced by quite significant depression in the glass transition temperature of the polymer as shown by differential scanning calorimetry. Maximum quantity of n‐hexane sorbed in the PS at 298 K and at a pressure close to saturation was about 12.4 wt %. The thermogravimetry yielded an isotherm with a strong hysteresis loop, explanation of which was hypothesized with the help of (a) Flory–Huggins sorption model extended by Vrentas, (b) analysis in terms of modification in the glass transition temperature of the n‐hexane/PS system as a function of sorbed quantity, and (c) change in total volume of the system. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1252–1258     

Rigid chain ribbon‐like metallopolymers

A set of new copolymers is here reported in which the repeating units are connected each other through Cu(II) metal centers. The coordination link is based on the bis‐chelating properties of salicylaldiminate groups of two different monomers. Due to their chemical structure, the two monomers afford, respectively, flexible and rigid repeating units in the metallocopolymers constitution upon coordination to copper centers. All the copolymers were soluble and easily processable. As shown by XRD analysis, rigid units' rich copolymers adopt a ribbon‐like structure in solid state in which highly planar strands of polymer stack thanks to π?π interactions, similarly to the polymer composed exclusively by rigid units. This behavior can be justified assuming the existence of a partial block character in copolymer constitution where long sequences of rigid units are alternated to sequences of flexible units. This assumption is supported also by DSC and UV–Vis analysis. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2412–2421