The optical intermediates of the low-temperature photopolymerization of TSHO diacetylene crystals

Hersel, W.; Sixl, H.; Wegner, Gerhard

doi:10.1016/0009-2614(80)80374-5

Cited by 26 publications

(5 citation statements)

References 20 publications

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“…Subsequent long wave UV-irradiation (335 < 1 < 380 nm) resulted in a further chain growth 112-141 and in the formation of polymer even at 4.2 K [14]. These experiments were carried out at temperatures 1.5 < T < 50 K and the intermediates were observed by UV/VIS-and ESR-spectroscopy 112 -14,17 -191.…”

Section: Main Propagation Effects In Related Diacetylenesmentioning

confidence: 99%

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Selfsensitization of the Photopolymerization of Diacetylenes Studied in Multilayers

Bubeck

Tieke

Wegner

1982

Ber Bunsenges Phys Chem

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Absorptionsspektren, sichtbar und ultraviolettThe photoreactivity of multimolecular Langmuir-Blodgett layers is studied with optical absorption spectroscopy. Whereas the polymerization of monomeric layers can be initiated by UV-irradiation only, irradiation of partially polymerized layers with visible light up to I 6 500 nm leads to a continuation of the reaction. The maximal polymer yield obtained with W-and visible light irradiation is the same. The action spectra of the chain growth of partially polymerized layers and of the photoconductivity correspond to each other. A new mechanism of the chain growth is proposed.

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Section: Main Propagation Effects In Related Diacetylenesmentioning

confidence: 99%

“…The explanation given to these earlier observations was the following [I2 - 14,191: The oligomers growing in the lattice of the monomer disturb the lattice sites adjacent to the chain ends. Therefore the energy level of these monomers adjacent to chain ends are lowered.…”

Section: Main Propagation Effects In Related Diacetylenesmentioning

confidence: 99%

Selfsensitization of the Photopolymerization of Diacetylenes Studied in Multilayers

Bubeck

Tieke

Wegner

1982

Ber Bunsenges Phys Chem

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“…This requires a high commensurability of monomer and polymer lattices, which is a key reason why diacetylenes turned into beautiful and attractive study objects. Several laboratories performed investigations towards unraveling the polymerization mechanism at low temperatures using XRD and UV‐spectroscopy [88–91] . Most importantly, Sixl et al .…”

Section: Linear Polymerizationmentioning

confidence: 99%

“…Several laboratories performed investigations towards unraveling the polymerization mechanism at low temperatures using XRD and UV-spectroscopy. [88][89][90][91] Most importantly, Sixl et al achieved a detailed characterization of individual reaction intermediates by applying optical absorption and EPR spectroscopy. [42,92] They showed the photochemically triggered diacetylene polymerization in the SC to be more complex process than one might have anticipated.…”

Section: Linear Polymerizationmentioning

confidence: 99%

What Changes in Topochemistry when Going from Small Molecule Dimerizations to Polymerizations in Single Crystals?

Salzillo

Brillante

Weber

et al. 2023

Helvetica Chimica Acta

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This publication promotes the increased necessity for strain management in topochemical reactions with an enlarged structural extension of the molecular products formed, i. e., when going from small molecule dimerizations, through linear polymerizations to the formation of 2D polymers. Further, it promotes to combine the trap model for photon absorption with concrete molecular scale consequences of this absorption on topochemical transformations and briefly discusses the expected consequences topological dimensionality of the forming (macro)molecular products has on trap location. The time appears ripe for going in this direction because local information concerning structural changes within single crystals is now accessible by the 3D‐ΔPDF method. This method greatly facilitates the analysis of diffuse X‐ray scattering providing access to concrete values of pair distribution functions and, thus, factual information on which and how distances change near a reaction site. Although only based on a first case where distance changes could be quantified in a lateral polymerization, the thoughts put forward may ignite more research towards a full understanding of all the action that occurs when a photochemically triggered topochemical reaction takes place. The 3D‐ΔPDF method is so attractive for this purpose because it provides otherwise inaccessible local information in pair correlation functions rather than average structure information, which is used through the ubiquitous Bragg scattering.

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“…[ 17 ] Then a series of oligomers with chain lengths ranging from dimer to decamer are formed, which can sensitize chain propagation reaction even upon irradiation with visible light. [ 18 ] In our previous works, we have reported that spin angular momentum of CPUV, [ 19 ] magnetochiral dichroism, [ 20 ] chiral nanoparticles, [ 21 ] and chiral dopants [ 22 ] are all capable of imparting a chiral bias for the photopolymerization of DA during photoinitiation, and among them, the interaction between chiral source, especially CPUV, and DA dimer is considered to play a key role in the enantioselective synthesis of helical polydiacetylene (PDA). On the other hand, circularly polarized visible light (CPVL) can typically manipulate the chiral torsion between DA molecules in supramolecular systems, which would eventually self‐assemble and accumulate into helical aggregates [ 23 ] while in the process of helical PDA chain propagation, whether asymmetric photopolymerization can be achieved through the CPVL endowed chiral imbalance to regulate, remains a question to be answered.…”

Section: Introductionmentioning

confidence: 99%

Selectively Regulating Asymmetric Photopolymerization Via Competition Between Circularly Polarized UV and Visible Light

Zhang

Feng

Xie

et al. 2023

Advanced Optical Materials

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an example, these polymers block with polythiophene and self-assemble into single-handed helical nanostructures twisted by nanofibers, showing excellent self-ordering, self-classification, and tunable photoluminescence characteristics. [4] Generally, it is noteworthy that relevant asymmetric synthesis requires a chiral bias, including one enantiomer of chiral reactant, [5] chiral catalyst, [6] chiral solvent, [7] or some suitable macroscopic or microscopic chiral field, such as stirring [8] and template. [9] Compared to traditional matter-to-matter chirality transfer based on the use of chiral reactant or catalyst, utilizing the physical light-matter interaction for enantioselective synthesis of helical polymer using CPL as the chiral source has attracted considerable interests since it is inherently chiral and has been regarded as one hypothesis for the evolution of homochirality in nature. CPL has been widely applied in asymmetric photolysis, photosynthesis of chiral organic compound as well as asymmetric polymerization to obtain optical active substance, [10] modulate the helical structure in polymers [11] and supramolecular system, [12] and regulate the chiral morphology of quantum dots and gold nanoparticles. [13] Although great advances have been obtained in CPL-triggered asymmetric photochemical reactions, the enantioselectivity obtained in most cases is ultimately limited owing to the small Kuhn anisotropy factor. In this sense, there is good motivation to find generic mechanisms to promote enantioselective light-matter interaction and photon-to-matter chirality transfer. Therefore, helical conjugated polymer is a very interesting template due to the initiation and chain propagation processes involved in their photopolymerization, which can often be mediated by different wavelengths of light. [14] Despite there are a lot of reports focusing on realizing asymmetric photopolymerization through single circularly polarized ultraviolet light (CPUV) in this field, the combination of the two chiral biases has not been explored yet.The photopolymerization of diacetylene (DA) has been widely used as model systems to study photochemical mechanism which is characterized by a variety of reaction intermediates. [15] Of particular advantage is the absence of disorder, which is always present in homogeneous solution reactions Circularly polarized light (CPL) has attracted considerable interest since it can impart chiral bias into photochemical reactions and open up a novel opportunity for synthesizing chiral polymer materials. Despite numerous reportsdescribing the chiral induction effect with single CPL, the synergistic or competitive effect between two types of CPL-i.e., circularly polarized ultraviolet light (CPUV) for triggering asymmetric polymerization while circularly polarized visible light (CPVL) only for accelerating helical chain propagation-is rarely reported. Here, this work demonstrates that the selective regulation on the asymmetric photopolymerization can be realized by the arbitrarily coupled irradia...

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The optical intermediates of the low-temperature photopolymerization of TSHO diacetylene crystals

Cited by 26 publications

References 20 publications

Selfsensitization of the Photopolymerization of Diacetylenes Studied in Multilayers

Selfsensitization of the Photopolymerization of Diacetylenes Studied in Multilayers

What Changes in Topochemistry when Going from Small Molecule Dimerizations to Polymerizations in Single Crystals?

Selectively Regulating Asymmetric Photopolymerization Via Competition Between Circularly Polarized UV and Visible Light

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