材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
ポリビニルアルコール (PVA) の光酸化における化学構造変化と電気伝導の関係
青木 弘行大橋 秀行鈴木 邁
著者情報
ジャーナル フリー

1975 年 24 巻 257 号 p. 129-136

詳細
抄録

In the evaluation of the photo-oxidation of plastic materials, little discussions have been made on the correlation between the physical properties and the change of chemical structure during the photo-oxidation.
We have previously studied the kinetics of the photo-oxidation of poly (vinyl alcohol) and reported that the scission and crosslinking of polymer chain are frequently accompanied with the formation of carbonyl groups.
The present report deals with the correlation of the carbonyl group content of the photo- oxidized poly (vinyl alcohol) with the temperature dependence of the electrical conductivity and the frequency of the scission of the polymer chain.
The results obtained are as follows
(1) The absorption peaks of intramolecular band (3275cm-1), α, β-unsaturated aldehyde (1682cm-1), ester (1165cm-1) and trans ethylene (965cm-1), all of which are absent in case of solid phase photo-oxidation, are observed during the liquid phase photo-oxidation. The easiness of formation of carbonyl groups is in the order of ketonic, aldehydic, acidic and esteric type in the first stage of the photo-oxidation, and in the order of aldehydic, ketonic, acidic and esteric in the later stage.
(2) In the liquid phase photo-oxidation, dehydration occurs first and the photo-oxidation is remarkably accelerated by the chain scission and crosslinking which have resulted from the formation of carbonyl groups. Also, the keto-enol tautomeric structure appears as the photo-oxidation proceeds.
(3) Scission of polymer chain is considered to be random from the results of the change in the number average of polymerization degree with time.
(4) The rate of mean molecular scission exhibits two stages in the course of photo-oxidation, being closely related to the formation of carbonyl groups (aldehydic, ketonic and acidic type).
(5) A good correlation exists between the mean molecular scission and the carbonyl concentration. As the activation energy of chain scission is in fair agreement with that of the formation of carbonyl groups, the chain scission seems to be associated with the formation of carbonyl groups.
(6) The temperature dependence of volume electrical current exhibits a three-step change. The variation of volume electrical current calculated from this change is found to be related with the carbonyl concentration. This may arise from the generation of electron carriers as carbonyl groups are formed and their migration along the π-electron system with the hopping mechanism. This result seems to indicate the possibility of electronic conduction in addition to the usual ionic conduction in the photo-oxidized poly (vinyl alcohol).

著者関連情報
© 日本材料学会
前の記事 次の記事
feedback
Top