Soluble Polydiacetylene Research Articles

Absorption spectra of chemically modified soluble poly-diacetylene

Spectral changes in poly(3BCMU)/CHCl 3 solutions induced by UV-irradiation were examined in relation with the extent of chain scission yielding oligomers and of Cl addition. Acetone soluble oligomer fractions exhibited an absorption peak at 2.9 eV. Chain scission was dominant for the high molecular weight fraction, while Cl addition was dominant for the oligomer fractions. The Cl addition did not affect the absorption peak but reduced the absorbance of the solutions, until the extent of halogenation reached a high level. However, the spectra of cast films shifted significantly to the high energy side even by a small level of halogenation.

Rod to coil transition and aggregation in soluble polydiacetylenes: Semidilute regime

Visible absorption, rheological measurements, polarizing light microscopy, and temperature–time dependent quasielastic light scattering was used to examine the dilute–semidilute properties of polydiacetylene solutions, specifically poly(4BCMU). A good (tetrahydrofuran) and poor (toluene) solvent were selected for examining solution properties over a broad range of solvent quality. In this particular instance, poly(4BCMU) dissolved in both the pure solvents and their respective mixtures. Based on the observation that dramatic color changes (yellow–orange–red) can occur with the hydrodynamic radius remaining invariant, it is quite likely that the color changes are due to a local modification in the conjugation length. That is, on a molecular level, a local stiffening of the segments occurs as the magnitude of the red absorption component increases. Interestingly, the stability of the solutions towards aggregation/phase separation also correlates well with the absorbance value of the red peak. Furthermore, careful thermal aging measurements confirm that as the aggregation process proceeds, the absorption spectrum remains unchanged, although the initially relatively broad spectral peaks do become significantly easier to resolve. As a result, an ‘‘intermediate’’ peak (due to an intermediate conjugation length) in the orange region is resolvable. Finally, polarized light microscopy confirms that the aggregates formed from thermally aged solutions containing an orange/red component are highly anisotropic, indicative of high chain alignment. Similar results are obtained from evaporating off the solvent from a dilute yellow solution. The implications of this self-alignment process are discussed.

Thermal effects in picosecond optical phase conjugation in soluble polydiacetylene

Degenerate four-wave mixing of picosecond laser pulses in a polydiacetylene/toluene solution is reported. Phase conjugate reflectivities of 500% and larger are reported. The dominant mechanism is found to be a thermally induced refractive index grating in the solvent.

Soluble polydiacetylenes for picosecond nonlinear optical phase conjugation

Soluble polydiacetylenes are used as a nonlinear medium for picosecond degenerate four-wave mixing. Thermally induced refractive-index changes and a large ultrafast Kerr effect are experimentally observed and analysed theoretically.

Absorption and Fluorescence Spectra of Polydiacetylenes (4BCMU and 3BCMU) in Solution

Absorption and fluorescence spectra have been measured on soluble poly-diacetylenes (4BCMU, 3BCMU), having the side group R=n-BCMU (n-butoxy carbonyl methyl urethane, n=4, 3), in chloroform/n-hexane mixture solvents for various solvent compositions and temperatures. The observed features of the absorption spectra are interpreted by assuming that two types of the coil-to-rod conformational transition take place in the two distinct isomeric bond-structures, which presumably correspond to the acetylenic and butatrienic types, respectively. Experimental phase-diagrams are presented as functions of solvent composition and temperature. Fluorescence bands were observed in rod-like polymer solutions at low temperatures. It is suggested that these largely Stokes-shifted emission bands are due to the self-trapped π-π * excitons on the one-dimensional polymer chains.

Picosecond degenerate four-wave mixing in soluble polydiacetylenes

The observation of optical phase conjugation utilizing the intrinsic Kerr-like nonlinear susceptibilities of two soluble polydiacetylenes is reported. Phase conjugate reflectivities of up to 40% were observed on a timescale of ≲100 ps and a value of χ(3)xyyx =7×10−12 esu evaluated.

Some new examples of polymer modification

This lecture summarizes some of our recent results about reactions with synthetic polymers. By cationic ring-opening polymerization of 4H, 7H-1,3-dioxepin a linear polyacetal containing one C-C-double bond per repeating unit is obtained. Copolymerization of this monomer with trioxane or dioxolane is possible. Various addition reactions can be carried out with these unsaturated polyacetals, polymeric epoxides being of special interest. Some other unsaturated cycloacetals are briefly mentioned. Amide moieties in linear polyamides can be modified by different reactions. Preparation and properties of poly-N-chloroamides and poly-N-trifluoroacetyl-amides are described. By reaction of metalated polyamides with alkyl halides poly-N-alkylamides are available. Anionic grafting reactions can also be carried out. Reduction of the amide groups leads to the formation of polyminoalkylenes. By topochemical polymerization of esters of 10,12-docosadiyne-1, 22-diol soluble polydiacetylenes are obtained. These polymers react in homogeneous solution with SbCl5 or FeCl3. Furthermore the hydrolysis of the ester groups and the reacylation is described.

Spectroscopic studies of polydiacetylene solutions and glasses. Glasses of a hydrogen-bonding polymer

In this communication we report some electronic spectral studies on a soluble polydiacetylene: poly[4,6-decadiyne-1,10-bis-(butoxycarbonyl methylene urethane)], 4BCMU. The results obtained are comparable to our previous studies on another soluble polydiacetylene: poly[10,12-docosadiyne-1,22-bis-(phenyl acetate)], 9PA. The essential difference between these two systems is that 4BCMU contains sidegroups capable of forming hydrogen bonds parallel to the polymer chain whereas the 9PA sidegroups cannot.

Spectroscopic studies of polydiacetylene solutions and glasses

Absorption, fluorescence excitation and emission spectra of a soluble polydiacetylene, obtained by the solid-state polymerization of the bis-(phenyl acetate) ester of 10,12-docosadiyne-1. 22-diol, have been recorded at room and liquid-nitrogen temperatures for different solvents. Spectral shifts, similar to those reported for other soluble polydiacetylenes, are observed on addition of a non-solvent or on cooling the solutions. The fluorescence quantum yield was measured from 2-methyl tetrahydrofuran solution at room temperature. The yield, was roughly one hundred times larger for this system at 77 K and well-structured fluorescence spectra were observed for this low-temperature glass.

Solved and Unsolved Problems in the Solid-State Polymerization of Diacetylenes

Abstract Knowledge of the conversion dependence of the molecular weight and molecular weight distribution is necessary in order to understand the mechanism of polymerizations. Until recently the determination of molecular weights has been an unsolved problem in the area of the solid-state polymerization of diacetylenes. In this paper a survey is given of experiments on the solution properties of two soluble polydiacetylenes. The polydiacetylene chain behaves in solution like a random coil of worm-like chains with typical persistence length of 15O Å. The yellow-to-blue transition in P3BCMU was found to be connected to an aggregation process.

Some Soluble Polydiacetylenes Derived from 10, 12-Docosadiyn-1, 22-Diol

Abstract Synthesis and physical properties of some new soluble polydiacetylenes obtained by solid state polymerization of derivatives of 10,12-Docosadiyn-1,22-diol(1) are described.

Visual conformational transitions of water soluble polydiacetylenes: Effects of pH and electrolyte on absorption and fluorescence spectra

Visual conformational transitions (yellow↔red or purple) of some water soluble polydiacetylenes (RC–C≡C–CR)x, where R=–(CH2)3,4OCONHCH2COO−K+ and –(CH2)2,3COO−K+, which is analogous to the helix↔coil conformational transition of polypeptides are reported. The conformational transitions, nonplanar↔planar (or twisted) is introduced by varying the concentration of an electrolyte and the pH, and are characterized by the absorption and emission spectroscopy. The yellow solutions of polydiacetylenes turn red or purple upon increasing the concentration of an electrolyte such as KCl and upon lowering the pH, from-12 to 2. The electrolyte concentration dependent absorption spectra display an isosbestic point at 471 nm. No isosbestic point is observed during pH titration. Explanations are forwarded for this discrepancy. The yellow solutions of all the polymers are found to fluoresce. Depending on the side groups used, the red or purple solutions either fluoresce with a substantial reduction in intensity or do not fluoresce at all. Fluorescence maxima show dependence on λexc when the side group R=Pxn(CH2)2,3COO−K+. Also the maxima of the corrected fluorescence excitation spectra of such polymers are found at different wavelengths than the maxima of the corresponding absorption spectra.(AIP)