Journal of Polymer Science: Polymer Symposia最新文献

Various halogen substituted poly (1,3-phenylene-isophthalamide)s have been prepared. Their glass transition temperature T_g (DSC), thermal decomposition courses (TGA), and flame resistance (oxygen index) are discussed.

The polyamides substituted with halogen in the meta position to NH group showed higher T_g and better thermal stability than those substituted with the same halogen in the ortho position. All halogenated polyamides studied had fairly good flame resistance characteristics: high oxygen indices and high char yields. Halogenated aromatic polyamides with nitrogen ortho to halogen showed the flammability characteristic: limiting oxygen index = 38 + 61 × (weight loss at initial plateau temperature).

DDA measurements made over a wide frequency range with a novel sensor are used to determine the onset of reaction, variation in viscosity, onset of gel, and reaction completion in a series of peroxide-initiated unsaturated polyester resins diluted in styrene monomer. The dielectric measurements provide detailed insights into (he the cure process not available by conventional thermographic techniques.

The polymerization and characterization of the ether-containing aromatic polyimides of the following general structure are presented.

The polymerization was conducted in one step in homogeneous solution of m-cresol at high temperatures. Typical polyeterimides (PEI) were noncrystalline and showed excellent thermal stability. Among 46 polymers synthesized, only two were crystalline. PEI had glass transition temperatures from 178° to 277°C and exhibited excellent processibility. Many PEI were also soluble in dipolar aprotic solvents and chlorinated hydrocarbons.

The thermal decomposition of polyethylene terephthalale has been examined by healing isothermally in a high-mass reaction chamber and collecting the evolved acetaldehyde on a GC column for quantization. Kinetics were determined at lime intervals up to 1 h for temperatures 225°C, 240°C, 250°C, 260°C, 265°C, 270°C, 280°C, and 300°C. The rate of acetaldehyde evolution was found to be directly proportional to time of reaction at each temperature, thus fitting a zero-order reaction. The Arrhenius plot of the data yielded a straight line above the melting point with a slope different from the straight line for reaction rates below the melting point. The change in slopes occurred around the crystalline melting point. The following thermodynamic values were found above and below the melting point, respectively: E_A, 37.5 and 8.2 kcal/mol; ΔS_A, + 1.5 and −54 e.u.; A, 0.68 × 10¹⁴ and 0.43 × 10² sec⁻¹. Possible mechanistic implications are discussed.

2-Vinyllhiolane-1,1-dioxide (Ia) and 2-vinylthiane-1,1-dioxide(Ib) have been prepared and polymerized with free radical initiators to obtain poly(sulfonyl-hex-2-enylene) (IIa) and poly(sulfonyl-hept-2-enyIene-co-2-vinylthiane-1,1-dioxide) (IIb), respectively, via a ring-opening mechanism. Structures of the polymers are supported by infrared and ¹H-NMR spectroscopy. Poly(sulfonyl-hex-2-enylene) was insoluble in ordinary organic solvents, but soluble in concentrated sulfuric acid or trifluoroacetic acid, and was white amorphous powder, softening at 168°C. Degradation occurred at 294°C under N₂. Ia copolymerized with certain vinyl monomers, such as ethyl acrylate, but its copolymerization behavior was different from those of normal vinyl monomers.

The electron transfer reaction from excited phenanthrene to acceptors was shown to be modified markedly when the phenanthrene unit was covalently linked to polyelectrolytes. (1) Such functionalized polyelectrolytes were shown to form hydrophobic microdomains in aqueous solution. (2) Uptake of amphiphilic acceptor substrates by the microdomain was demonstrated and was shown to accelerate the forward electron transfer reaction. (3) The electrostatic effect of microdomain was shown to effect the photoinduced charge separation. (4) The electrostatic potential of the microdomain was estimated to be comparable with that of surfactant micelles.

Polymers of β-cyclodextrinyl substituted styrene and 4′-oligodimethylsiloxanyl-4-vinyldiphenyl were synthesized. Their oxygen perm selectivity was studied from the viewpoint of investigating the effects of the introduction of bulky p-substituents to polystyrene on their permeation behaviors. The bulky substituents were quite effective in enhancing the permeability; however, the selectivity in permeation decreased with the increase in permeability.

The primary carbenium salt 9-anihranylmethyl hexafluorophosphate is characterized by ¹H- and ¹³C-NMR spectroscopy. The results show that in the temperature range −60°-15°C the initiator exists as a classical carbenium ion and a protonated anthracenium ion. At higher temperatures the reactions of self-alkylation and disproportionation proceed, giving bianthracenes, hydroanthracenes, and other dimer forms.

The polymerization of α-methylstyrene and p-methoxystyrene, initiated by 9-anthranylmethyl hexafluorophosphate, is investigated. The mechanism of initiation, the stereochemical configuration, and the end groups of the polymer chains are determined.

Three novel main-chain polyarninimides were prepared containing rigid and/or flexible groups within the backbone. The polymer precursors were initially synthesized from bis-dimethylhydrazides and dihalides at room temperature through the Menschulkin reaction, which yielded hydrazinium ionenes. In a similar fashion, low molecular weight model compounds were also prepared in order to confirm the structures of the ionene polymers. It was found that the ionenes were totally, or at least partially, converted o the aminimide form in the presence of water alone, while the model cationic compounds required a strong base before conversion to their corresponding aminimides. These new polymers were characterized by (heir infrared and NMK spectra, as well as dilute solution viscosity. Preliminary solution properties indicate that the hydrazinium form of the polymers behave as poly electrolytes, whereas the aminimide form behaves as a neutral polymer.