Polyepoxides; formation and properties of their network structure

A discussion on epoxy resin network formation and properties with emphasis on study of the mechanisms of epoxide polymn. via phosphorescence and NMR spectroscopic methods. [on SciFinder (R)

Photoinitiated cationic polymerization; a study to the polymerization and molecular mobility of polyepoxide networks using phosphorescence spectroscopy

The rate of network formation in the polymn. and crosslinking of 1-epoxyethyl-3,4-epoxycyclohexane, 1,4-butanediol diglycidyl ether, 3,4-epoxycyclohexylmethyl-3',4'-epoxy cyclohexane carboxylate, and cyclohexene oxide in the presence of di(4-tert-butylphenyl) iodonium hexafluoroarsenate photoinitiator was characterized by the increase in the intensity of fluorescence (lmax = 340 nm) and phosphorescence (lmax = 480) emissions. The half life of the triplet excited state was const. during polymn. which indicated that the increase in crosslink d. proceeded via an inhomogeneous pathway. The phosphorescence intensity and half life of all epoxy networks showed a discontinuity in their Arrhenius plots at .apprx.260 K due to the onset of quenching of the triplet excited state. The activation energy above the transition temp. was an indication of the increase in chain mobility with increasing temp. Dynamic thermomech. anal. of the networks established a correlation between the mech. properties and chain mobility

Singlet oxygen oxygenation of enol ethers; the synthesis of optically active 1,2-dioxetanes. II

(+)-(Methoxymethylene)fenchane I (R = H, R1 = OMe) on singlet O oxidn. gave dioxetanes II and III, which on thermal decompn. underwent chemiluminescence in which (+)-fenchone was the only chemiluminescent species at lmax 420 nm. Photosensitized oxygenation of I (R = OMe, R1 = H) also gave 2 isomeric 1,2-dioxetanes. I were prepd. by Wittig methoxymethylenation of (+)-fenchone. Adamantanone (IV) on Wittig methoxymethylenation, followed by singlet O oxidn. gave dioxetane V, which on thermal decompn. gave only IV and HCO2Me and a bright blue chemiluminescence with lmax 420 nm and k1 2.96 * 10-3 s-1 at 79.9 Deg in decane. The prepn. of the dioxetanes allows the comparison of light- and chem. induced circular polarization of luminescence. [on SciFinder (R)

Chirality solely due to the presence of an excited state

2-(Methoxymethylene)adamantane-4-one (I) was photoautoxidized to the dioxetane II (69% enantiomer excess); II decompd. thermally to give chiral excited 2,4-adamantanedione (III), the decay of which to achiral ground state III was characterized by circular polarization chemiluminescence. The racemization of excited III and the intramol. energy transfer assocd. with its decay are related to the UV and circularly polarized CD of III and the CD of III-18O. [on SciFinder (R)

Molecular mobility of polyepoxide networks as revealed by emission spectroscopy and mechanical analysis

The use of phosphorescence spectroscopy was used to reveal the mol. mobility of polyepoxide networks. The polyepoxides were prepd. by a photoinitiated cationic polymn. and crosslinking of (cyclo)aliph. bisepoxides. The emission properties were studied as a function of temp. Both phosphorescence intensity and triplet excited state half-life showed a discontinuity in their Arrhenius plots. For all networks this discontinuity was situated at .apprx.260 K and was due to the onset of quenching of the triplet excited state. The activation energy above the transition point was characteristic of the individual networks and was an indication of the increase in motion as the temp. was raised, ultimately leading to a simultaneous motion of large parts of the network. From these emission data the glass transition temp. and the width of the glass transition region were estd. The mech. properties of the network were established with dynamic mech. thermal anal. (DMTA) measurements. A striking correlation between mol. mobility (from emission data) and mech. properties (from DMTA) was obsd. [on SciFinder (R)

Polyimide

The invention relates to a polyimide substantially built up from monomeric units of 3,3',4,4'-benzophenonetetracarboxylic dianhydride and monomeric units of a primary aliphatic diamine. The polyimide according to the invention is characterized in that the primary aliphatic diamine is substantially 1,4-diaminobutane. The thermal stability of the polyimide according to the invention has surprisingly been found to be very good. Owing to this very good thermal stability, the polyimides according to the invention can very well be processed at - relatively - high processing temperatures without any appreciable thermal degradation of the polyimide. As a result, the polyimides processing potential has increased considerably. Also, articles made of the polyimides according to the invention can be used at significantly higher temperatures. Said articles have very good mechanical properties. Articles containing a polyimide are suited for being used in the most diverse applications. Application within a large number of industries may be thought of, such as the electrical, electronic and automotive industries. In space travel, too, the interest in such polyimides is great