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A series of phthalimide-and 1,12-benzoperylene-1′,2′-dicarboxylic imido-linked alkynes were prepared and analyzed by UV, FT-IR, optical microscopy, and differential scanning calorimetry. The possibility to convert ω-alkynes (R-(CH 2)n-CtCH) to diacetylenic compounds (R-(CH2)nCtC-CtC-(CH2)n-R) was investigated for R ) phthalimide and 1,12-benzoperylene-1′,2′-dicarboxylic imide with n ) 1, 3, and 9. Formation of the diacetylenic compound is usually straightforward (as checked by comparison with independently synthesized diacetylenes), and in some cases heat-induced polymerization of the thusformed diacetylenes proceeds directly. For the perylene imide-linked materials with n ) 1 and n ) 3 1,2-polymerization occurs, while for n ) 9 1,4-polymerization occurs. The 1,4-polymerization is also observed for the phthalimide-linked materials. For R ) phthalimide and n ) 1 this 1,4-polymerization can only be induced by further heating, while for the analogous n ) 9 compound 1,4-polymerization is already induced by UV-vis irradiation at room temperature. This is related to the flexibility of the methylene spacer in the crystal.

A series of phthalimido-substituted (Pht) diacetylenes with the structure Pht-(CH2)n-Ct C-CtC-(CH2)m-R was synthesized. The influence of the length of the alkyl spacer n between the phthalimido group and the diacetylene group, the length of the alkyl spacer m and an additional polar group R on the thermal and UV-induced polymerization was investigated by systematic variation of n, m, and R (for R ) H and m ) 8, n ) 1, 3, 4, 5, 8, 9; for n ) 9 and m ) 3, R ) H, CH2OH, COOH). All synthesized compounds underwent thermal polymerization. The polymerization temperature increased with longer n spacer or shorter m spacer, and no effect was observed on variation of R. For UV-induced polymerization, a spacer length n of more than four carbon atoms was necessary. Introduction of a hydrogen-bond-forming hydroxyl or carboxyl group at the other side of the diacetylene yielded polymers with a significantly higher degree of conjugation and also improved film formation on quartz enormously.

The photopolymerization of spin-coated films of diacetylene derivatives containing phthalimido or naphthaldiimido moieties has been studied by monitoring the increase in the optical absorption in the visible region on irradiation at 308 nm. The phthalimido derivatives form blue polymers with absorption maxima at ca. 630 nm, corresponding to a highly conjugated, close to planar polydiacetylene (PDA) backbone configuration. The naphthaldiimido derivative yields a red polymer with an absorption maximum at 535 nm, indicating a backbone structure with a substantially reduced degree of π-bond conjugation. The initial, “low-dose” quantum yields for monomer conversion, based on the total number of photons absorbed at 308 nm, range from 2 to 20. Monomer conversions up to ca. 50% are found. The polymerized films are found to be photoconductive using the time-resolved microwave conductivity technique (TRMC). Mobile charge carriers are suggested to be formed via the triplet state of the arylimido moieties which undergoes long-distance charge transfer to polydiacetylene chains to form the arylimido radical anion and the mobile PDA radical cation or “hole”. A maximum value of 1.4 × 10-2 cm2/(V s) for the product of the quantum yield for charge carrier formation and the hole mobility is found. The photoconductivity of the “blue” polymer is approximately an order of magnitude larger than for the “red” variety. This is attributed to a higher mobility of PDA holes in the former compound, resulting from the higher degree of backbone conjugation. The lifetime of the mobile carriers extends well into the microsecond region, which is considerably longer than previously found on direct ionization of PDA chains.

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