Mari Inoki

Synthesis and properties of novel aromatic polyamides containing 2-methyl-4,5-oxazolediyl structure

Abstract Novel aromatic polyamides having 2-methyl-4,5-oxazolediyl units in the main chains were synthesized. The polyamides were prepared from 4,5-di(4-aminophenyl)-2-methyloxazole (DAPMO) and/or 4,4′-[4,5-(2-methyl) oxazole]dibenzoic acid (MODBA) by the direct polycondensation method. The polyamides, the inherent viscosities of which ranged from 0.64 to 1.95 dl g −1 , were obtained almost quantitatively. The polyamides indicated high thermal properties: glass transition temperatures were found in the range between 280 and 354°C, and thermal decomposition temperatures ranged from 376 to 421°C. The polyamides exhibited good solubility in many organic solvents such as m -cresol, N,N -dimethylacetamide, 1-methyl-2-pyrrolidone, N,N -dimethyl formamide and conc. H 2 SO 4 at 2.0% (w/v). All the polyamides showed amorphous nature. The introduction of the zigzag, rigid and polar 2-methyl-4,5-oxazolediyl structure into the main chains of polyamides was effective in improving the solubility without lowering the high thermal properties.

CURING BEHAVIOR AND PROPERTIES OF EPOXY RESINS CURED WITH THE DIAMINE HAVING HETEROCYCLIC RING

ABSTRACT Diamines having heterocyclic ring, 4,5-bis (4-aminophenyl)-2-phenyl-imidazole (BAPI), 4,5-bis(4-aminophenyl)-2-methyloxazole (BAPO) and novel diamine, 2,3-bis(4-aminophenyl)benzo[g]quinoxaline (BABQ) were prepared as curing agents for epoxy resin. Epoxy resins were obtained by curing diglycidyl ether of bisphenol A (DGEBA) with the above diamines. Properties of these DGEBA-diamine systems were studied and compared to that of DGEBA cured with commercially available diamine, 4,4′-diaminodiphenyl sulfone (DDS). On differential scanning calorimetry (DSC), the peaks of exotherms of the mixtures of DGEBA with these diamines having heterocyclic rings were observed at lower temperature and these reactions were completed in shorter time than that of DGEBA with DDS. The epoxy resins cured with these diamines containing heterocyclic ring showed excellent bonding strength even at high temperature and thermal resistance, e.g., DGEBA-BABQ gives greater bonding strengths as 35.1, 30.0, and 26.2 MPa when tested at 20, 120, and 180°C, respectively and residual weight at 600°C was 44% after being cured at 160°C for 2 hours. In the curing of DEGBA-BAPI, the reaction was accelerated and completed in a shorter time, but the bonding strength lowered somewhat, since the tertiary amine in the imidazole ring acts as catalytic curing agent which leads to epoxy homopolymerization.

Thermal polymerizations of alkali 4-(2-bromoethyl)benzoates in bulk

Thermal polymerizations of alkali 4-(2-bromoethyl)benzoates (2-BEBAs) were investigated. The polymerization of the lithium salt at 220°C for 2 h under reduced pressure in bulk, followed by esterification, produced poly(methyl 4-vinylbenzoate), having a number-average molecular weight (Mn) of 9500 in a 54% yield. Thus, elimination of hydrogen bromide to form a double bond occurred, followed by vinyl polymerization. In contrast, polymerization of the potassium salt at 200°C for 2 h afforded poly(oxycarbonyl-1,4-phenylene-ethylene) (polyester 1), having an inherent viscosity of 0.19 dL g−1 in a 95% yield: i.e., polycondensation proceeded to afford the polyester. Reaction of the sodium salt at 220°C for 2 h produced polyester 1 having Mn of 4000 in a 28% yield as well as 4-vinylbenzoic acid in a 9% yield. In the reaction of the sodium salt, both polycondensation and double bond formation occurred. Thus, these polymerizations depended on the counter cations of 2-BEBAs.

Thermal polymerizations of alkali and alkaline earth 4-vinylbenzoates in bulk

Thermal polymerizations of alkali and alkaline earth 4-vinylbenzoates (4-VBAs) in bulk were investigated. The relative reactivity of the alkali salts decreases in the following order: K > Na > Li, which is in reverse order to that of alkali methacrylates. In the polymerization of K-4-VBA at 240°C, the number-average molecular weight decreases with increasing reaction time, although the yield of polymer increases. The polymerization of the K salt proceeds as long as the crystallinity of the monomeric salt is maintained, and is terminated when there is no crystalline compound in the reaction mixture left. The relative reactivity of the alkaline earth salts decreases in the following order: Mg > Ca > Sr >> Ba. The polymerization of Mg-4-VBA proceeds rapidly at 240°C in the initial stage (30 min) and then levels off, however, the appearance of the reaction mixture still remains crystalline.

Metal adhesive properties of polyamides having the 2,3‐bis(1,4‐phenylene)quinoxalinediyl structure

Polyamides were synthesized by interfacial polycondensation of 2,3-bis(4-chloroformylphenyl)quinoxaline (BCFPQ) and several aliphatic diamines using a phase transfer catalyst, and their adhesive property for stainless steel was investigated. The inherent viscosity of the obtained polyamides ranged from 0.37 to 1.24 dL g−1. The glass transition temperatures of the polyamides ranged between 154 and 201°C, and their thermal decomposition temperatures were above 450°C. The polyamides were soluble in several organic solvents, including m-cresol, N-methyl-2-pyrrolidone (NMP), and formic acid. The adhesive property for stainless steel was examined by a standard tensile test. One member of the series, polyamide P8, derived from BCFPQ and 1,8-octanediamine, displayed high tensile strength with values of 232 kgf cm−2 at 20°C, 173 kgf cm−2 at 120°C, and 137 kgf cm−2 at 180°C. Thus, the tensile strength of P8 decreased at 180°C, but the decrease was much smaller than that of an epoxy resin in wide use as a metal adhesive. Heat distortion temperature, measured by thermal mechanical analysis, of P8 was 191°C. This suggested that P8 possessed high thermal resistance in metal adhesives.

Synthesis and Properties of Polyamides and Polyimides Derived From Diamines Having 2-Phenyl-4,5-Oxazolediyl Units and Polyamide/Montmorillonite Composite

Aromatic polyamides were synthesized from 4,5-bis(4-aminophenyl)-2-phenyloxazole (APO) or 4,5-bis[4(4-aminophenoxy)phenyl]-2-phenyloxazole (APPO) containing 2-phenyl-4,5-oxazolediyl units with several aromatic carboxylic dichlorides by a low-temperature solution polycondensation method. The polyamides were obtained quantitatively, and their inherent viscosities ranged from 0.48 to 1.25 dL g−1. The glass transition temperatures (T gs) were displayed between 234 to 311°C, and the residual weight at 600°C (Res.wt600) exceeded 52% in nitrogen atmosphere. The polyamides showed good solubility in several aprotic polar solvents, such as N,N-dimethylacetoamide (DMAc), N-methyl-2-pyrrolidone (NMP), and dimethyl sulfoxide (DMSO). Aromatic polyimides were derived from APO or APPO with aromatic carboxylic dianhydrides through polyamic acids. The inherent viscosities of the polyamic acids, which were 0.53 to 1.02 dL g−1, T gs of the polyimides were observed between 259 to 361°C and their Res.wts600 were above 70%. The polyamides and polyimides were amorphous and afforded thin, flexible and tough films. We also prepared a nanocomposite of the polyamide derived from APPO with organophilic montmorillonite clay.

Preparation and Properties of Novel Aromatic Polyamides from Diamines Containing 4,5-Imidazolediyl Structure

Novel aromatic polyamides were prepared from aromatic diamine containing 4,5-imidazolediyl unit, either by low temperature solution polycondensation or by direct polycondensation. Used diamines were 4,5-bis(4-aminophenyl)-2-phenylimidazole 1, 4,5-bis[4-(4-aminophenyl)]-2-(4-methylphenyl)imidazole 2 and 4,5-bis[4-(4-aminophenoxy)phenyl]-2-phenylimidazole 3. The obtained aromatic polyamides were produced with moderate to high inherent viscosity and soluble in polar aprotic solvents such as N,N-dimethylacetamide (DMAc), 1-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). Thermogravimetric analysis showed those polymers were stable up to 422°C in nitrogen atmosphere. The glass transition temperature (T g)s of the polymers derived from diamine 3 were in the range between 243 and 275°C, and these values were approximately 120–160°C lower than those analogue polyamide I series containing no phenoxy units. The properties of polyamide I series are also compared with those of analogue polymers that order of aromatic nuclei and amide linkage is reversible.

METAL ADHESIVE PROPERTIES OF POLYAMIDES HAVING 4,5-DI(1,4-PHENYLENE)-IMIDAZOLEDIYL STRUCTURE

Polyamides were synthesized by the direct polycondensation of aromatic diamines containing 4,5-imidazolediyl structure with aliphatic dicarboxylic acids, and the metal adhesive properties of these polymaides were studied. The inherent viscosity of the obtained polyamides was in the range of 0.28 to 0.71 dl g−1. The decomposition temperatures (T ds) of the obtained polyamides were above 400°C and their glass transition temperatures (T gs) were from 168 to 198°C. These polyamides also showed good solubilities in polar solvents, such as N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAc) and formic acid. A standard tensile test was performed in order to examine the adhesive property of these polyamides for stainless steel, and the obtained polyamides showed excellent tensile strengths, e.g. polyamide P1s derived from 4,5-di(4-aminophenyl)imidazole (DAPI) and sebasic acid had values of 212 kgf cm−2 at 20°C, 183 kgf cm−2 at 120°C, and 133 kgf cm−2 at 180°C. A commercially available epoxy resin was also examined, and showed great tensile strength at 20°C. However, the strength of the epoxy resin was found to decrease with increasing temperature, whereas polyamide having 4,5-imidazolediyl structure retains its strength at temperatures of up to 180°C. In addition, the polyamide was also derived from 4,4″-diamino-o-terphenyl(DAOT) (rather than DAPI) and sebasic acid, and the properties of the polyamides derived, respectively from DAPI and DAOT were compared.

Thermal dimerization of alkali and alkaline earth acrylate–but-3-enoate and methacrylate–but-3-enoate binary systems in the solid state

The solid state thermal reaction of binary salts obtained from a solution of an equimolar mixture of alkali or alkaline earth salts of but-3-enoic acid and methacrylic acid (3-BA–MA), after conversion to the methyl ester, gave mainly dimethyl (E)-hex-1-ene-1,5-dicarboxylate as a novel cross-coupled dimer. The highest conversion (62.2%) to the cross-coupled dimer was obtained using the potassium salts on heating at 230 °C for 2 h. Similarly, the methyl ester of the cross-coupled dimer, dimethyl (E)-pent-1-ene-1,5-dicarboxylate, was obtained from the salts of 3-BA and acrylic acid (AA), however a small amount on an isomeric ester dimethyl (E)-pent-2-ene-1, 5-dicarboxylate was also obtained. The X-ray diffraction patterns of potassium 3-BA–MA and potassium 3-BA–AA indicate the presence of a new phase, different from that of the individual salts. The selective cross-coupled dimerization, without rearrangement of 3-BA to crotonic acid, polymerization and crosslinking, was due to the new crystal phase of the binary salts as well as to the formation of solid solution crystals between the monomeric salts and the dimeric salt.