Radiolysis of poly(acetaldehyde‐co‐chloral): A positive E‐beam resist

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Abstract
Acetaldehyde and chloral were copolymerized using triethyl aluminum catalyst. The copolymer (ACC) obtained with equimolar monomer feed is not alternating in structure as it was once thought to be; it is comprised of two fractions differing in MW and composition. ACC has good thermal stability which is further improved by endcapping. Radiolysis in vacuo caused depolymerization with a G(M) value (number of monomers produced per 100 eV) of about 4000 to 80% completion. The G(S) value for chain scission is 1.9. These processes are effectively inhibited by benzoquinone. Oxygen markedly increases G(M) to ca. 18,000 and > 97% completion. Addition of tetrabutyl ammonium salt or tetramethyl urea has no effect on the depolymerization, whereas the addition of di‐t‐butyl‐p‐cresol causes an induction period after which normal unzipping ensues. Even UV photolysis of ACC in the presence of oxygen produces monomer with a quantum yield of 1.7, but very little photolysis occurs in the absence of oxygen. Gamma radiolysis sensitized by (C6H5)2IPF6 has G(M) value of 32,700. These results are very similar to the radiolysis and photolysis of the homopolymer of monochloroacetaldehyde and reinforce the mechanisms proposed for them. The E‐beam sensitivity of ACC is about 3 × 10−6 C cm−2.