Synthesis,structure, and characterization of nematic liquid‐crystalline thermosets based on bisacrylates

Four bisacrylate mesogenic monomers and the corresponding liquid‐crystalline thermosets were synthesized. The chemical structures of the intermediate compounds and monomers obtained were confirmed by elemental analyses, Fourier transform infrared, and ¹H NMR and ¹³C NMR spectra. The mesomorphic properties and thermal stability were investigated with differential scanning calorimetry, thermogravimetric analysis, polarized optical microscopy, and X‐ray diffraction measurements. The influence of the curing temperatures and time on the phase behavior and thermal stability of the thermosets was discussed. All the monomers and thermosets exhibited a nematic schlieren texture. However, the monomers only showed the melting transition, and the thermosets displayed the glass transition. The experimental results demonstrated that the monomer structures strongly affected the phase behavior and the curing reaction rate, and the glass‐transition temperatures and thermal stability of the thermosets increased with the curing temperature and time. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4478–4485, 2005     

Facile,one‐pot synthesis of aromatic diamine‐based benzoxazines and their advantages over diamines as epoxy hardeners

Three aromatic diamine‐based benzoxazines were successfully prepared by a facile, clean, one‐pot procedure from 1,4‐phenylenediamine ( 1 ), 4,4′‐diaminodiphenyl ether ( 2 ), and 4,4′‐diaminodiphenyl methane ( 3 ), respectively. Their structures were confirmed by NMR spectra and single crystal diffractogram. The effect of the reactivity of diamines on the purity of the resultant benzoxazines was discussed. The resultant benzoxazines were applied as hardeners for cresol novolac epoxy (CNE). The processing window, the latent curing characteristic, and the miscibility of benzoxazine/CNE systems were discussed. Compared with diamines ( 1 and 3 ), ( 1 and 3 )‐based benzoxazines show latent curing characteristic as epoxy hardeners, and wide processing windows can be obtained. Compared with diamine ( 2 ) which is immiscible with CNE in the molten state, ( 2 )‐based benzoxazine shows good miscibility with CNE. Dynamic mechanical analysis shows the T_gs of the benzoxazine/CNE thermosets are as high as 242–243 °C. Thermogravimetric analysis shows the outstanding thermal stability of the resultant thermosets. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2430–2437, 2010     

Butadiene–isoprene copolymerization with V(acac)3‐MAO. Crystalline and amorphous trans‐1,4 copolymers

Butadiene‐isoprene copolymerization with the system V(acac)₃‐MAO was examined. Crystalline or amorphous copolymers were obtained depending on isoprene content. Both butadiene and isoprene units exhibit a trans‐1,4 structure and are statistically distributed along the polymer chain. Polymer microstructure, comonomer composition, and distribution along the polymer chain were determined by ¹³C and ¹H NMR analysis. The thermal and X‐ray behaviors of the copolymers were also investigated and compared with results from solid‐state ¹³C NMR experiments. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4635–4646, 2007     

Synthesis and crosslinking reaction of a novel polymer containing benzoxazine and phenyleneethynylene moieties in the main chain

A novel polymer, poly( 1 ) containing benzoxazine and phenyleneethynylene moieties in the main chain with number‐average molecular weights ranging from 1400 to 9800 was obtained quantitatively by the Sonogashira–Hagihara coupling polymerization of the corresponding iodophenyl‐ and ethynylphenyl‐substituted monomer 1 . Poly( 1 ) was heated at 200 °C under N₂ for 2 h to obtain the cured polymer, poly( 1 )′ via the ring‐opening polymerization of the benzoxazine moieties. The structures of the polymer before and after curing were confirmed by ¹H‐NMR, IR, and UV–vis absorption and reflectance spectroscopies. Poly( 1 )′ was thermally more stable than monomer 1 and poly( 1 ). A specimen was prepared from a mixture of poly( 1 ) and phenol‐diaminodiphenylmethane type benzoxazine 2 by heating at 200 °C for 2 h under N₂. The poly( 1 )/ 2 resin was thermally stable than bisphenol‐A type benzoxazine resin 3 . Poly( 1 ) exhibited XRD peaks corresponding to the d‐spacings of 1.26–0.98 and 0.40 nm, assignable to the repeating monomer unit and alignment of polymer molecules, respectively. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2581–2589     

Facile preparation of novel epoxy curing agents and their high‐performance thermosets

Two flame‐retardant epoxy curing agents, 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐yl‐tris(4‐hydroxyphenyl)methane (1) and 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐yl‐ (4‐aminophenyl)‐bis(4‐hydroxyphenyl)methane (2), were prepared by a facile, economic, one‐pot procedure. The structures of the curing agents were confirmed by IR, high‐resolution mass, 1‐D, and 2‐D NMR spectra. A reaction mechanism was proposed for the preparation, and the effect of electron withdrawing/donating effects on the stabilization of the carbocation was discussed. (1‐2) served as curing agents for diglycidyl ether of bisphenol A (DGEBA), dicyclopentadiene epoxy (HP‐7200), and cresol novolac epoxy (CNE). Properties such as glass transition temperature, coefficient of thermal expansion, thermal decomposition temperature, and flame retardancy of the resulting epoxy thermosets were evaluated. The resulting epoxy thermosets show high T_g, low thermal expansion, moderate thermostability, and excellent flame retardancy. The bulky biphenylene phosphinate pendant makes polymer chains difficult to rotate, explaining the high T_g and low thermal expansion characteristic. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7898–7912, 2008     

Synthesis of a new hyperbranched‐linear‐hyperbranched triblock copolymer and its use as a chemical modifier for the cationic photo and thermal curing of epoxy resins

A new hyperbranched‐linear‐hyperbranched polymer was prepared in a one pot process by reaction of 4,4‐bis(4‐hydroxyphenyl)valeric acid and poly(ethylene glycol) (HPH). After characterization by ¹H and ¹³C NMR, SEC, DSC, and TGA, this polymer was used, in proportions of 5, 10, and 15 phr, as a chemical modifier in the UV and thermal cationic curing of 3,4‐epoxycyclohexylmethyl‐3′,4′‐epoxycyclohexyl carboxylate epoxy resin. The curing process was studied by calorimetry, demonstrating the accelerating effect of the hydroxyl groups present in HPH's structure. The morphology of the resulting thermosets depended on the curing system used, as demonstrated by FE‐SEM microscopy, but in both cases phase separation occurred. Thermosets obtained by thermal curing presented lower thermal stability than UV‐cured materials. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

A New Ferrocene‐Containing Polyamide Prepared from an Improved Synthesis of 1,1′‐Ferrocene Dicarbonyl Chloride and Ferrocene‐Based Diamine

1,1′‐Ferrocene dicarbonyl chloride was prepared by an improved and efficient conversion method from 1,1′‐ferrocene dicarboxylic acid and reacted by esterification with p‐nitrophenol, followed by reduction, to form a ferrocene‐based diamine, 1,1′‐ferrocene bis (p‐amino phenylate). The diamine was characterized by elemental analysis, ¹H NMR, and Fourier transform infrared (FTIR) spectroscopy and subsequently condensed with 1,1′‐ferrocene dicarbonyl chloride to form a novel main chain ferrocene‐containing polyamide, poly{imino ferrocene bis (p‐amino phenylate) ferrocenyl}. Its polymeric nature was confirmed by its physical properties, elemental analysis, FTIR spectroscopy, differential scanning calorimetry, and thermogravimetric studies.     

Epoxy resin curing reaction studied by proton multiple‐quantum NMR

This study demonstrates that the curing reaction of thermosetting polymers, in particular, epoxy resins cured with aliphatic amines, can be characterized by different multiple‐quantum (MQ) NMR experiments performed in low‐field spectrometers. Measurements of the curing reaction at 40 °C, 70 °C, and 100 °C are carried out to obtain the kinetic parameters like induction time, vitrification time, polymerization rate, and activation energy being consistent with data obtained by other traditional and complementary techniques. Besides, it is demonstrated that ¹H MQ‐NMR spectroscopy is a successful approach to overcome the experimental challenge arising from the characterization of high dipolar‐coupled polymers to study the network structure and segmental dynamics of thermosetting polymer networks. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1324–1332     

Facile one‐pot/one‐step technique for preparation of side‐chain functionalized polymers: Combination of SET‐RAFT polymerization of azide vinyl monomer and click chemistry

An azido‐containing functional monomer, 11‐azido‐undecanoyl methacrylate, was successfully polymerized via ambient temperature single electron transfer initiation and propagation through the reversible addition–fragmentation chain transfer (SET‐RAFT) method. The polymerization behavior possessed the characteristics of “living”/controlled radical polymerization. The kinetic plot was first order, and the molecular weight of the polymer increased linearly with the monomer conversion while keeping the relatively narrow molecular weight distribution (M_w/M_n ≤ 1.22). The complete retention of azido group of the resulting polymer was confirmed by ¹H NMR and FTIR analysis. Retention of chain functionality was confirmed by chain extension with methyl methacrylate to yield a diblock copolymer. Furthermore, the side‐chain functionalized polymer could be prepared by one‐pot/one‐step technique, which is combination of SET‐RAFT and “click chemistry” methods. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis of novel diene polymer via friedel–crafts‐type reaction of polybutadiene with aromatic compounds

This study describes a novel and facile synthesis strategy for a styrene‐butadiene rubber (SBR)‐like polymer via Friedel–Crafts‐type reaction between aromatic compounds and polybutadiene using an aluminum chloride as a catalyst. Although gelation was induced by a reaction of a generated carbocation with olefins in other polybutadiene chains in benzene and toluene because of their low electron densities on their rings, anisole with a higher electron density reacted with the polybutadiene carbocation efficiently. The introduction ratio of anisole increased as the reaction proceeded, and the obtained polymer, BRAN polymer, contained 15% anisoles for olefins in the polybutadiene in 4 h at 80 °C as estimated by ¹H NMR analysis. The glass‐transition temperature (T_g) of the BRAN polymer also increased with anisole content (T_g ~?50 °C when anisole contents 20%). The vulcanizate containing the BRAN polymer showed higher mechanical properties compared to samples using other matrix polymers. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 841–847     

Ferrocene compounds. XXV. Synthesis and characterization of ferrocene‐containing oligoamides,their precursors,and analogues

A general method for preparation of ferrocene‐containing monoamines (5–7) and diamines (10, 11) starting from the corresponding quaternary ammonium iodide 3 and ferrocene mono‐ (4) and dithiaaliphatic acids (8, 9) was developed. Amines obtained have been characterized as acet‐ and benzamides (12–15). The oligoamide precursors (16, 17, 22, 23) were synthesized by reactions of succinic or glutaric anhydride with amines (6, 7, 10, 11). Their conversion into oligoamide analogs (20, 21, 25) failed. The desired diamides (20, 21) were prepared by condensation of amines (6, 7) with alkanedioyl chlorides, (CH₂)_n(COCl)₂ (n = 0, 1, 2, 3). Reactions of diamine 10 with succinic or glutaric anhydride gave amino acids 28—formal monomers for the planned oligomerization. Oligomers 29 were synthesized by condensation of equimolar amounts of diamines 10 and the above mentioned alkanedioyl chlorides in dichloromethane at 0°C. The structure of oligomers 29 was indicated from their IR and ¹H‐NMR spectra in comparison with the model substances 12–28. The degree of polymerization of compounds 29 was determined by ¹H‐NMR end‐group analysis (DP_n = 4–6). © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 25–36, 1999     

Tailoring the liquid crystalline property via controlling the generation of dendronized polymers containing azobenzene mesogen

The first‐ and second‐generation dendronized polymers containing azobenzene mesogen were designed and successfully synthesized via free radical polymerization. The chemical structures of the monomers were confirmed by elemental analysis, ¹H NMR, and ¹³C NMR. The molecular characterizations of the polymers were performed with ¹H NMR and gel permeation chromatography. The phase structures and transition behaviors were studied using differential scanning calorimetry, polarized light microscopy, and small‐angle X‐ray scatter experiments. The experiment results revealed that the first‐generation dendronized polymer exhibited liquid crystalline behavior of the conventional side‐chain liquid crystalline polymer with azobenzene mesogen, that is, the polymer exhibited smectic phase structure at lower temperature and nematic phase structure at higher temperature. However, the second‐generation dendronized polymers exhibited more versatile intriguing liquid crystalline structures, namely smectic phase structure at lower temperature and columnar nematic phase structure at higher temperature, and moreover, the phase structure still remained before the decomposition temperature. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1149–1159, 2010     

High Tg and high organosolubility of novel unsymmetric polyimides

A series of new polyimides (PIs) containing di‐tert‐butyl side groups were synthesized via a polycondensation of 1‐(4‐aminophenoxy)‐4‐(4‐amino‐2‐methylphenyl)‐2,6‐di‐tert‐butylbenzene ( 3 ) with various aromatic tetracarboxylic dianhydrides. The novel unsymmetric PIs exhibited a low dielectric constants (2.78–3.02), low moisture absorption (0.53–1.35%), excellent solubility, and high glass transition temperature (308–450 °C). The PI derived from the new diamine and the very rigid naphthalene‐1,4,5,8‐tetracarboxylic dianhydride (NTDA) was soluble in N‐methyl‐2‐pyrrolidone, chloroform, m‐cresol, and cyclohexanone. The unsymmetric di‐tert‐butyl pendent groups significantly enhance the rotational barrier of the polymer chains; thus these PIs had high T_gs. The ¹H NMR spectrum of the diamine 3 revealed that the protons of 4‐aminophenoxy moiety are not chemical shift equivalent. This is because the steric hindrance of the bulky di‐tert‐butyl groups prevents the benzene ring of 4‐aminophenoxy moiety from rotating freely. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2443–2452, 2009     

Side‐chain conformational changes during the thermoshrinking process: γ‐Ray polymerization and spectroscopic study of uncrosslinked poly(methacryloyl‐Ala‐OMe)

Poly(methacryloyl‐L ‐alanine‐methyl ester) (1) has an optically active side chain and consists of thermoshrinking hydrogels upon crosslinking. We synthesized an uncrosslinked polymer of 1 by the γ‐ray polymerization method. For the prepared polymer, variable‐temperature circular dichroism (CD) and ¹H NMR spectra were studied, and we found conformational changes in the optically active side chains during the thermally induced phase transition. Intense CD spectra reveal ordered conformation in the side chain of 1 below the phase transition temperature (∼28 °C). A well‐resolved ¹H NMR spectrum of 1 at 0 °C shows that the conformational angles in the polymer side chain are fixed at low‐energy minima. With increasing temperature, the frozen side chain starts rotating vigorously and takes an unordered orientation. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2671–2677, 2000     

Stereoregular polyamides entirely based on tartaric acid

Two new stereoregular polyamides, namely PTA‐LL and PTA‐LD, derived from (2S,3S)‐(−)‐2,3‐dimethoxy‐1,4‐butanediamine and (2R,3R)‐(+)‐ or (2S,3S)‐(−)‐2,3‐dimethoxybutanedioic acid are described. The two diastereoisomeric polymers contain two pairs of stereocenters in the main chain of the repeating unit, one in the diamine and the other in the diacid counterpart. L and D refer to the configuration of the tartaric acid unit from which they proceed. These polyamides were prepared by polycondensation in solution and were fully characterized by elemental analysis, DSC, and IR/NMR spectroscopies. Number average molecular weights around 30,000 were estimated by GPC and viscosimetry. Both compounds are soluble in water and display large optical activity. CD and ¹H‐NMR measurements in chloroform solution suggested the presence of definite secondary structures in this solvent. Solid samples were found to crystallize upon annealing and the crystal structure of both polyamides was investigated by X‐ray diffraction. PTA‐LL crystallized in an orthorhombic lattice in the space group P22₁2₁ whereas PTA‐LD seemed to adopt a P1 triclinic structure. In both cases the polymer chain appears to be in a folded conformation more contracted than in the common γ‐form of conventional nylons. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 983–993, 1999     

Ordered nanostructures at two different length scales mediated by temperature: A triphenylene‐containing mesogen‐jacketed liquid crystalline polymer with a long spacer

A mesogen‐jacketed liquid crystalline polymer (MJLCP) containing triphenylene (Tp) moieties in the side chains with 12 methylene units as spacers (denoted as PP12V) was synthesized. Its liquid crystalline (LC) phase behavior was studied with a combination of solution ¹H NMR, solid‐state NMR, gel permeation chromatography, thermogravimetric analysis, polarized light microscopy, differential scanning calorimetry, and one‐ and two‐dimensional wide‐angle X‐ray diffraction. By simply varying the temperature, two ordered nanostructures at sub‐10‐nm length scales originating from two LC building blocks were obtained in one polymer. The low‐temperature phase of the polymer is a hexagonal columnar phase (Φ_H, a = 2.06 nm) self‐organized by Tp discotic mesogens. The high‐temperature phase is a nematic columnar phase with a larger dimension (a′ = 4.07 nm) developed by the rod‐like supramolecular mesogen—the MJLCP chain as a whole. A re‐entrant isotropic phase is found in the medium temperature range. Partially homeotropic alignment of the polymer can be achieved when treated with an electric field, with the polymer in the Φ_H phase developed by the Tp moieties. The incorporation of Tp moieties through relatively long spacers (12 methylene units) disrupts the ordered packing of the MJLCP at low temperatures, which is the first case for main‐chain/side‐chain combined LC polymers with MJLCPs as the main‐chain LC building block to the best of our knowledge. The relationship of the molecular structure and the novel phase behavior of PP12V has implications in the design of LC polymers containing nanobuilding blocks toward constructing ordered nanostructures at different length scales. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 295–304     

Synthesis,characterization, and thermal properties of ladderlike polyepoxysiloxanes

Starting from trichlorosilanes and using 1,4‐phenylenediamine as a template, we have synthesized some ladderlike poly(glycidyl‐co‐alkyl/aryl)siloxanes (polyepoxysiloxanes or polyepoxies for short). The structures of copolymers were confirmed through IR, ¹H NMR, elemental analyses, and gel permeation chromatography. Curing behaviors of these polyepoxies in the absence and presence of a curing agent have been studied with DSC. It was shown that these epoxies could be cured without any curing agent. Copolymers having aromatic groups showed higher curing reactivity than those having alkyl groups. The experimental results also demonstrate that the curing reaction occurred solely via epoxy functionality, not via the condensation reaction of the hydroxy groups located at the end of polymer main chains. The thermal stability of the cured polymers was examined by thermogravimetric analysis. The results confirm that polyepoxies with aromatic groups had better thermal stability than those with alkyl groups. It was also found that polyepoxies cured with a diamine have a higher thermal stability than those cured in the absence of a curing agent. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2215–2222, 2001     

New copolymers of a tautomerizable β‐ketonitrile monomer: Synthesis,characterization and solution tautomerism

The monomer 2‐methyl‐3‐oxo‐5‐phenyl‐4‐pentenonitrile (MOP) was prepared by reaction of ethyl cinnamate and propionitrile in alkaline mixture. This monomer exhibits three possible tautomeric forms. The tautomeric equilibria of MOP and its copolymers with styrene in different solvents were analyzed by ¹H NMR spectroscopy. The bulk and solution radical copolymerization initiated with azobisisobutyronitrile was carried out at 60 °C. The products were characterized by ¹H NMR, ¹³C NMR, HSQC NMR, HMBC NMR, and FTIR spectroscopies. The weight‐average molecular weight and polydispersity index were analyzed with size exclusion chromatography. The monomer reactivity ratios were obtained with the Fineman‐Ross method, obtaining a value of r₁r₂ = 0.286. MOP copolymer composition as well as the nature of the solvent significantly affected the tautomeric equilibrium. Regression analysis of the copolymer composition with solvatochromic parameters showed a good linear correlation, as quantitatively expressed by means of the linear solvation energy relationship using the empirical set of Kamlet‐Taft solvent parameters. This behavior could be attributed to polymer–polymer or polymer‐solvent interactions prevalent in solvents of different polarity, which are responsible for changes in macromolecular chain conformations, as confirmed by FTIR and viscometric studies. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis and Properties of Polycarbosilanes Having Lactose‐Derived Structures

A polycarbosilane having lactose‐derived structures was synthesized, and its thermal property, cytotoxicity, chemical crosslinking, and protein adsorption properties were investigated. The polycarbosilane (PSB‐Lac) was prepared by a thiol‐ene reaction between precursor poly(1‐(3‐butenyl)‐1‐methylsilacyclubane) (PSB) and heptaacetyl lactose that carried a thiol group at the anomeric position, and the successive deprotection of the acetyl groups. The lactose introduction efficiency determined by ¹H NMR measurement was 75%. TGA and DSC revealed that the polymer had a 5 wt% decomposition temperature of 260 °C and glass transition temperature (T_g) of 84 °C, which indicated that PSB‐Lac was a thermally stable polymer. PSB‐Lac had no significant cytotoxicity, which was evaluated by human liver cancer cell line HepG2 cultivation on the polystyrene dishes coated with the polymer. Urethane‐crosslinked PSB‐Lac films were prepared by casting solutions of PSB‐Lac and hexamethylene diisocyanate and heating at 120 °C after evaporation of the solvent. The crosslinked PSB‐Lac showed higher adsorption of bovine serum albumin than the similarly crosslinked polycarbosilane that had a glucose structure (PSB‐Glc). © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2420–2425     

Synthesis and study of the thermal crosslinking of bis(m‐aminophenyl) methylphosphine oxide based benzoxazine

Bis(m‐aminophenyl)methylphosphine oxide based benzoxazine (Bz‐BAMPO) was obtained using a three‐step synthetic method from the aromatic diamine and 2‐hydroxybenzaldehyde as starting materials. The structure and purity of the monomer was confirmed by elemental analysis, FTIR, ¹H NMR, ¹³C NMR and ³¹P NMR spectra. The curing kinetics of Bz‐BAMPO was investigated by nonisothermal differential scanning calorimetry (DSC) at different heating rates and by FTIR spectroscopy. The isoconversional method was used to evaluate the dependence of the effective activation energy on the extent of conversion. The evolving factor analysis (EFA) method was applied to the spectroscopic FTIR data obtained in monitoring benzoxazine homopolymerizations. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7162–7172, 2008