Studies on the thermotropic liquid crystalline polymer. XII. Synthesis and properties of crosslinkable thermotropic liquid crystalline homo- and copoly(ether-ester)s

A series of crosslinkable thermotropic liquid crystalline poly(ether-ester)s and copoly(ether-ester)s was prepared. All of the polymers were crosslinked by thermal treatment or photo-irradiation upon heating. The thermal stability and thermal crosslinking reaction of these polymers were investigated. These polymers also could be crosslinked by copolymerization with vinyl monomers, such as styrene or methyl methacrylate. The crosslinked polymers exhibited thermotropic liquid crystalline behavior after softening by heating. The phase behavior of linear polymers and crosslinked polymers was studied by differential scanning calorimetry (DSC) and an optical polarizing microscope equipped with a heating stage. © 1995 John Wiley & Sons, Inc.     

Preparation and thermal properties of polyquinazolones: Effect of the chemical structure of bisbenzoxazinones on the thermal properties

Four kinds of polyquinazolones were synthesized from 4,4′-diaminodiphenylether and bisbenzoxazinones having different central aromatic nuclei (benzene, biphenyl, benzophenone, diphenylmethane). All the polymers were prepared by solution polycondensation at 190°C at a concentration of 15% solid in m-cresol, and were obtained with intrinsic viscosities in the range of 0.3–0.8 dL/g in 97–98% yield. Their thermal properties were studied by using dynamic thermogravimetry and isothermal weight loss. All the polymers were found to produce high char yields (55–75%) in nitrogen. Oxidative thermal stability of the polymers was dependent on the chemical structure of bisbenzoxazinone and was governed by the stability of the bonds in the quinazolone units. The following order of oxidative thermal stability of the quinazolone units was determined from this study: diphenylmethane < benzophenone < biphenyl < benzene.     

Synthesis,optical, electrochemical and electroluminescent properties of novel fluorene-alt-bithiophene copolymers bearing phenylvinyl bridged accepting side chains

Two-dimensional poly[fluorene-alt-bithiophene] backboned copolymers were prepared by introducing phenylvinyl bridged accepting side chain containing malononitrile, 1,3-indanedione, or 4-nitrophenyl acetonitrile accepting moiety. The structural, optical, electroluminescent, electrochemical properties of these polymers were studied in details. These polymers possess good thermal stability and low highest occupied molecular orbital (HOMO) level (−5.59 to 5.67 eV). Results show that the introduction of π-conjugated accepting side chains can effectively adjust the optical and electrochemical properties of the resulting polymers. These new alternating copolymers may be promising electroluminescent materials.     

Synthesis and characterization of benzocyclobuten-4-yl acrylate monomer and its radical polymerization

<正>A benzocyclobuten-4-yl acrylate(1) monomer was prepared by esterification of 4-hydroxybenzocyclobutene with acryloyl chloride.The radical homopolymerization of 1 and copolymerization of 1 with styrene or n-butyl acrylate were carried out to produce linear polymers 2a,2b and 2c.Heating of these linear polymers under thermal initiation gave corresponding cross-linked polymers 3a,3b and 3c.The ring-opening reaction in the cross-linking process was confirmed by on-line infrared spectra.Differential scanning calorimetry showed that the glass transition temperatures of linear polymers 2a and 2b were 83.2℃and 68.1℃,respectively.Thermogravimetric analysis of the cross-linked polymers showed that they all exhibited good thermal stability.     

Thermal degradation behaviour of novel wholly para-oriented aromatic polyamide-hydrazides containing sulfone-ether linkages

Thermal stability and degradation behaviour of a series of novel wholly para-oriented aromatic polyamide-hydrazides containing flexibilising sulfone-ether linkages in their main chains have been investigated in nitrogen and in air using differential scanning calorimetry (DSC), thermogravimetry (TG), infrared spectroscopy (IR) and elemental analysis. All of these polymers have similar structural formula except for the presence of sulfone, ether, or sulfone-ether linking groups between appropriate aromatic nuclei in their main chains. The influence of incorporation of these linkages on the thermal stability and degradation behaviour of these polymers has also been studied. The polymers were prepared by a low temperature solution polycondensation reaction of 4-amino-3-hydroxybenzhydrazide (4A3HBH) and an equimolar amount of either 4,4′-sulfonyl dibenzoyl chloride (SDBC), 4,4′-[sulfonyl bis (1,4-phenylene)dioxy] dibenzoyl chloride (SODBC), 4,4′-[sulfonyl bis (2,6-dimethyl- 1,4-phenylene)dioxy] dibenzoyl chloride (4MeSODBC), or 4,4′-(1,4-phenylenedioxy)dibenzoyl chloride (ODBC) in anhydrous N,N-dimethyl acetamide (DMAc) as a solvent at −10 °C. A related polyamide-hydrazide without the flexibilising linkages is also investigated for comparison. It was synthesized from 4A3HBH and terephthaloyl chloride (TCl) by the same synthetic route. The results clearly reveal that these polymers are characterized by high thermal stability. Their weight loss occurred in three distinctive steps. The first was small and was assigned to the evaporation of absorbed moisture. The second was appreciable and was attributed to the cyclodehydration reaction of the o-hydroxy polyamide-hydrazides into the corresponding poly (1,3,4-oxadiazolyl-benzoxazoles) by losing water. This is not a true degradation, but rather a thermo-chemical transformation reaction. The third was relatively severe and sharp, particularly in air, and corresponded to the decomposition of the resulting poly(1,3,4-oxadiazolyl-benzoxazoles). There is a slight shift of the decomposition temperature of these polymers to a lower temperature as the sulfone-ether linkages were introduced into the polymer chains. The decomposition seems to start by breaking the sulfonyl groups as confirmed from DSC measurements. The results also indicate that the incorporation of the flexibilising linkages into the polymer main chains did not seem to significantly influence the thermal stability of these polymers in comparison with that of the polymer free from these linkages.     

Preparation and properties of polyamides and polymides containing bibenzyl,stilbene, and tolan structures

Polyisophthalamides and polyterephthalamides were prepared by the solution polycondensation of the corresponding diacyl chlorides with 4,4′-diaminobibenzyl, trans-4,4′-diaminostilbene, and 4,4′-diaminotolan in N,N-dimethylacetamide (DMAc). Polypyromellitimides were synthesized in two steps by the ring-opening polyaddition of pyromellitic dianhydride with the aromatic diamines in DMAc, followed by thermal cyclodehydration. The amorphous polyisophthalamides were soluble in some amide solvents containing lithium chloride, while the polyterephthalamides having fair degree of crystallinity were insoluble in these solvents. The thermal stability of these aromatic polymers decreased in the order of the tolan-containing polymers > the stilbene-containing polymers > the bibenzyl-containing polymers, both in air and under nitrogen.     

Effects of hydroxyvalerate contents in thermal degradation kinetic of cellulose acetate propionate/poly(3-hydroxyalkanoates) blends

Thermal stability of polymers is an important parameter that determines the application as well as the processing conditions. The green polymers have shown low thermal stability, such as the polyhydroxyalkanoates (PHAs). The PHAs with different comonomers containing hydroxyvalerate (HV) were studied. It was seen that the green polymer showed a fast thermal degradation process. The addition of the HV comonomer modified this profile and the thermal degradation kinetic. The blend prepared between the PHAs and other polymers can modify the thermal degradation process of the green polymers. In the present study, blends of cellulose acetate propionate and PHAs were prepared, and the thermal degradation kinetics of these blends were evaluated. It was observed that the cellulose acetate propionate (CAP) phase in the blends modified the thermal degradation process and kinetic profile of the PHA phase. In the blends, the thermal stability of the PHAs was slightly modified because of CAP reducing the reactivity of the PHAs. On the other hand, the thermal stability of the CAP phase in the blends is not largely modified by the PHA phase. However, the hydroxyvalerate comonomer decreases the reactivity of the CAP phase at the start of thermal degradation of the same. The interaction between the phases promotes the synergetic interaction, which slightly improves the thermal stability of the two polymers blends.     

Synthesis,characterization and properties of novel polyamides containing ferrocene unit and flexible spacers

Synthesis and characterization of ferrocene‐containing main‐chain polyamides are reported in this article. A new, interesting type of organometallic monomer (FDADO) based on ferrocene was prepared by interfacial condensation of 1,1′‐dichlorocarbonyl ferrocene with 2 mol 1,8‐diamino‐3,6‐dioxaoctane (DADO). A series of ferrocene‐based polyamides was prepared via polycondensation of the ferrocenyl diamine (FDADO) with different diacid chlorides using two different methods. The monomer and polymers were characterized by elemental analysis, infrared and NMR spectroscopy. The thermal stability and behavior of the synthesized polymers were evaluated by thermal gravimetric analysis (TGA), dynamic mechanical thermal analysis (DMTA), and differential scanning calorimetry (DSC). The crystallinity of polymers was examined by X‐ray diffraction analysis. Inherent viscosity, solubility and flame‐retardancy of the polymers were also studied. The obtained polymers showed good heat‐resistance and flame‐retardancy, and improved solubility vs generally reported polyamides in some common organic solvents. Copyright © 2007 John Wiley & Sons, Ltd.     

The preparation of non-extractable methylphenylpolysiloxane stationary phases for capillary column gas chromatography

Summary The synthesis of methylphenylpolysiloxane polymers and their use in the preparation of crosslinked, non-extractable stationary phases for fused-silica capillary columns are described. By preparing more viscous phenyl-containing polymers than are commercially available, stationary phase films of these polymers could be efficiently coated on fused-silica capillary columns and stabilized by a free radical crosslinking mechanism using peroxides. Four methylphenylpolysiloxane polymers containing different phenyl concentrations were prepared. These included three polymers containing 50% phenyl and one polymer containing 70% phenyl. Two of the 50% phenyl polymers had one phenyl and one methyl group attached to each silicon atom. One of these also had 1% vinyl incorporated. The third 50% phenyl polymer was synthesized in such a way that one half of the silicon atoms had two phenyl groups attached while the rest contained dimethyl groups. The 70% phenyl polymer also had 4% vinyl incorporated. Due to the intrinsic thermal stability of these phenyl phases and the enhanced film stability achieved by crosslinking, the 70% phenyl phase could be utilized up to 400 °C. Using the methods described in this paper, highly efficient and thermally stable fused silica capillary columns coated with crosslinked methylphenylpolysiloxane stationary phases can be successfully prepared.     

含1,3,4-噁二唑甲壳型液晶聚合物的合成与表征

甲壳型液晶聚合物（mesogen-jacketed liquid crystal polymer,MJLCP）是1987年由周其凤教授[1]首先提出的概念.从化学结构看,甲壳型液晶聚合物属于侧链型,由烯类单体经链式聚合制得,容易得到高分子量的产物,具有一般柔性侧链型液晶聚合物的一些优点.但是与柔性侧链型液晶聚合物不同的是,MJLCP分子中的刚性液晶基元是通过腰部或重心位置与主链相联结的,在主链与刚性液晶基元的侧基之间只有很短或者没有柔性间隔基.由于在这类液晶聚合物的分子主链周围空间内刚性液晶基元的密度很高,分子主链被由液晶基元形成的外壳所包裹并被迫采取相对伸直的刚性链构象.因此,这类液晶聚合物又和主链型刚性链液晶聚合物相似,具有较明显的链刚性.近年来,周其凤课题组围绕甲壳型液晶聚合物深入开展了分子设计与合成、分子结构与性能等多方面的研究.其中,设计合成具有特定功能的甲壳型液晶聚合物是在以往研究工作和学科交叉融合的基础上发展起来的一项新的研究工作.将一些有特殊功能的基团引入到甲壳型液晶聚合物中会使其具有崭新的特性.     

Sulfonated poly(ether sulfone)/sulfonated polybenzimidazole blend membrane for fuel cell applications

Polymer blending is used to modify or improve the dimensional and thermal stability of any two different polymers or copolymers. In this study, both sulfonated polybenzimidazole homopolymer (MS-p-PBI 100) and sulfonated poly(aryl ether benzimidazole) copolymers (MS-p-PBI 50, 60, 70, 80, 90) were successfully synthesized from commercially available monomers. The chemical structure and thermal stability of these polymers was characterized by ¹H NMR, FT-IR and TGA techniques. Blend membranes (BMs) were prepared from the salt forms of sulfonated poly(ether sulfone) (PES 70) and MS-p-PBI 100 using dimethylacetamide (DMAc). These blend membranes exhibited good stability in boiling water. The blending of 1 wt.% of MS-p-PBI 100 and 99 wt.% of PES 70 to produce the blend membrane BM 1 reduced membrane swelling, thus leading to good dimensional stability and comparable proton conductivity. Hence, BM 1 was chosen for the fabrication of a membrane electrode assembly (MEA) for proton exchange membrane fuel cell (PEMFC) and direct methanol fuel cell (DMFC) applications. This paper reports on PEMFC and DMFC performance under specific conditions.     

Synthesis and characterization of crosslinkable polyimides

A series of copolyimides were prepared from benzophenone-3,3′,4,4′-tetracarboxylic dianhydride (BTDA) and various aromatic diamines which contain a fluorenyl group and/or alkyl substituents in ortho position to the amine groups. The effect of the chemical composition on the glass transition temperature (T_g), thermal stability as well as on the dielectric constant of these polymers was studied. High T_g polymers (T_g ranging from 260 °C to 370 °C), withstanding temperatures as high as 400 °C for 10 h and having a low dielectric constant (from 2.6 to 3.1) were successfully synthesized. All these polymers were able to crosslink under UV or thermal treatments.     

Novel ferrocene modified poly(amide ether amide)s and investigation of physical and thermal properties

A new diamine containing ferrocene group with preformed ether and amide units was prepared via reaction of 1,1′-ferrocenedicarbonyl chloride with two moles of 2,6-bis(5-amino-1-naphthoxy)pyridine. Polycondensation reactions of the prepared diamine with different aromatic and aliphatic diacid chlorides in the presence of trimethylchlorosilane (TMSCl) resulted in preparation of novel ferrocene modified poly(amide ether amide)s. The monomer and polyamides were characterized and the effect of trimethylchlorosilane (TMSCl) as activating agent on the polymerization reaction was studied. The physical and thermal properties of the polyamides including inherent viscosity, solubility, thermal stability and behavior, flame-retardancy and crystallinity of the polymers were studied. The polymers showed good thermal stability and flame-retardancy, and also improved solubility in polar aprotic solvents.     

Thermal stability of aromatic polyesters prepared from diphenolic acid and its esters

The thermal performance of aromatic polyesters (poly(DPA-IPC), poly(MDP-IPC) and poly(EDP-IPC)) prepared from isophthaloyl chloride (IPC) with diphenolic acid (DPA) and its esters were studied with DSC and TG, and the decomposition mechanism of poly(DPA-IPC) were investigated using FTIR and integrated TG/FTIR analyses. As compared with ordinary aromatic polyesters, poly(DPA-IPC) has lower glass transition temperature (159 °C) and much lower thermal stability. It starts to decompose at about 210 °C and is characterized by two-stage thermal decomposition behavior, with active energies of decomposition of 206 kJ/mol and 389 kJ/mol, respectively. The analyses of the decomposition process and products indicate that the pendent carboxyl groups in poly(DPA-IPC) are responsible for its low thermal stability. Accordingly, a decomposition mechanism for the first stage is proposed. With this knowledge in mind, we capped the carboxyl groups in DPA with methyl and ethyl groups to prepare poly(MDP-IPC) and poly(EDP-IPC) from methyl diphenolate and ethyl dipenolate. As expected, these two polymers exhibit obviously improved thermal stability, with onset decomposition temperature of about 300 °C.     

Soluble,thermally stable,flame retardant quinoline-based poly(ester amide)s

A new diamine was prepared via reaction between 8-hydroxy-5-nitroquinoline and 4-nitrobenzoyl chloride, followed by reduction of the nitro groups of the resulted compound. Novel quinoline-based poly(ester-amide)s were produced through polycondensation reactions of the prepared diamine with different diacid chlorides. The monomer and poly(ester-amide)s were characterized and properties of the polymers including solution viscosity, thermal behavior and stability, solubility, and crystallinity were studied.

High thermal stability and improved solubility was observed for the polymers, indicating successful designing of monomer and related polymers for overcoming the main issue of thermally stable polymers, i.e. the problem of increasing solubility versus high thermal stability.

Also, by changing the diacid chlorides for the preparation of poly(ester-amide)s, the structure-property relations were investigated.     

High temperature polymers. III. Diphenyl sulfone-based polyamide-imides

High temperature thermoplastic polyamide-imides were prepared from a new series of aromatic diamines containing the diphenylsulfone unit and alternatively, oxydiphenyl and diphenylisopropylidene units. The polymers were prepared in their completely imidized form by using a facile in situ chemical imidization reaction which offers several advantages over the conventional thermal imidization process. The sulfone-based polyamide-imides exhibited an excellent combination of moldability, thermal stability, mechanical properties and solvent resistance. Analysis of the properties of these polymers in terms of structural variations permits a useful correlation of the effect of various structural units on performance. The polar diphenyl sulfone and amide-imide units increase the glass transition temperature and improve solvent resistance while the oxydiphenyl and diphenylisopropylidene units improve thermoplasticity. Sulfone ether diamine polyamide-imide (VI) offers the best combination of high temperature performance and moldability.     

Preparation and characterization of Co- and homopoly(phenylene etherimideketone)s

Poly(phenylene etherimdeketone)s were prepared by Friedel–Crafts acylation type polymerization using P₂O₅? CH₃SO₃H 1 : 10 (w/v) mixtures. Most of these polymers were semicrystalline. T_gS ranged from 203 to 236°C and crystalline melt temperatures were observed between 306 and 435°C. All of the polymers exhibited high thermal stability and good solvent resistance. © 1993 John Wiley & Sons, Inc.     

Thermal, mechanical and electrical properties of copper powder filled low-density and linear low-density polyethylene composites

Low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE) with different copper contents were prepared by melt mixing. The copper powder particle distributions were found to be relatively uniform at both low and high copper contents. There was cluster formation of copper particles at higher Cu contents, as well as the formation of percolation paths of copper in the PE matrices. The DSC results show that Cu content has little influence on the melting temperatures of LDPE and LLDPE in these composites. From melting enthalpy results it seems as if copper particles act as nucleating agents, giving rise to increased crystallinities of the polyethylene. The thermal stability of the LDPE filled with Cu powder is better than that for the unfilled polymer. The LLDPE composites show better stability only at lower Cu contents. Generally, the composites show poorer mechanical properties (except Young's modulus) compared to the unfilled polymers. The thermal and electrical conductivities of the composites were higher than that of the pure polyethylene matrix for both the LDPE and LLDPE. From these results the percolation concentration was determined as 18.7 vol.% copper for both polymers.     

Synthesis, characterization and photocrosslinking properties of polyacrylamides having bromo substituted pendant cinnamoyl moieties

New 3- and 4-bromocinnamoyl aniline were synthesized condensing 4-aminoacetophenone and the respective bromobenzaldehydes in the presence of sodium hydroxide. The monomers, 4-(3′-bromocinnamoyl) phenyl acrylamide (4,3′-BCPA) and 4-(4′-bromocinnamoyl) phenyl acrylamide (4,4′-BCPA) were prepared by reacting the respective chalcones and acryloyl chloride in the presence of triethylamine at 0-5 °C. Homopolymers of 4,3′-BCPA and 4,4′-BCPA was carried out in methyl ethyl ketone using benzoyl peroxide (BPO) under nitrogen atmosphere at 70 °C. The prepared polymers were characterized by UV, IR, ¹H-NMR and ¹³C-NMR techniques. The molecular weights (M_w and M_n) of the polymers were determined by gel permeation chromatography. The thermogravimetric analysis (TGA) of the polymers in nitrogen atmosphere reveals that they possess very good thermal stability required of a negative type photoresist. The glass transition temperature of poly(4,3′-BCPA) and poly (4,4′-BCPA) were found to be 55 and 64 °C respectively. The solubility of the polymers was tested in various polar and non-polar solvents. Photocrosslinking nature of the polymer samples was carried out in the presence and absence of various triplet photosensitizers in solution phase using chloroform solvent under medium frequency UV light. For using the polymers as negative photoresist materials the rate of photocrosslinking of the polymers was measured under the influence of different solvents, concentrations and position of the substituent.     

Polymer blend nanocomposites: effect of mercapto silane modified kaolin clay on the thermal properties of Polypropylene/Polystyrene blend

Nanocomposites based on polypropylene/polystyrene blends were prepared by melt mixing in a Thermo Haake Rheochord mixer. The effect of mercapto silane modified kaolin clay on the properties of nanocomposites has been studied. The characterization of polypropylene/polystyrene/clay nanocomposites was made by dynamic mechanical analysis, scanning electron microscope, and transmission electron microscopic, and the thermal stability was determined by using Thermogravimetric analysis. The activation energy of degradation was determined using three mathematical models, namely Horowitz–Metzger, Coats–Redfern and Broido's methods, and the results were compared. TGA results show an improved thermal stability for nanocomposite than the pure blend. The improvement in thermal stability of nanocomposites was confirmed by increasing the activation energy. Transmission electron microscopic observations showed that nanoclay layers were intercalated on the polymer matrix and were located at the interface between the two polymers Copyright © 2014 John Wiley & Sons, Ltd.