The bis(aryl)diacetylenes 1,4-bis(3-quinolyl)-1,3-butadiyne (1), 1,4-bis(4-isoquinolyl)-1,3-butadiyne (2), and 1,4-bis(3-pyridyl)-1,3-butadiyne (3) form strongly halogen bonded complexes with organic iodides, including tetraiodoethylene (TIE), 1,4-diiodotetrafluorobenzene (F4DIB), and 1,4-diiodooctafluorobutane (F8DIBut). The crystal structures for the new donor, 2, as well as for six complexes, 1·TIE, 1·F4DIB, 2·TIE, 2·F4DIB, 3·(F4DIB)2, and 3 2· (F8DIBut)2, are reported. Extended chain structures consisting of donor and acceptor molecules are observed in all cases, except that of 3 2·(F8DIBut)2, which forms a molecular adduct. In most cases, the complexes segregate into columns of donors and acceptors, as is typical for this class of complexes. However, 1·F4DIB displays an unusual “crosshatched” pattern with each acceptor directly above the diacetylene moiety of another donor along the b-axis. In addition to 1·F4DIB, 3 2·(F8DIBut)2 also exhibits packing that does not consist of segregated stacks (i.e., the acceptor in the chain sits on top of one end of the donor and the uncomplexed F4DIB sits on top of the other end). Neither diacetylene 2, nor any of the complexes, pack in a manner that would allow for topotactic polymerization of the diacetylene moiety.
For a number of different vulcanization systems, the equilibrium swelling ratios for carbon-black-filled and unfilled samples are shown to be linearly related, as found by Lorenz and Parks, indicating that the degree of crosslinking is not changed by incorporating carbon black. However, filled compounds swell less, and thus the apparent degree of crosslinking is significantly greater. For example, it is about twice as large for compounds containing 50 phr of HAF carbon black. This is confirmed by measurements of the elastic modulus of swollen samples. Relatively strong bonds appear to be formed between rubber molecules and the surface of carbon black particles - bonds that can withstand swelling stresses and temperatures of up to 120 °C. Bonding between rubber and carbon black is also indicated by the limited swelling of filled rubber compounds even before vulcanization, although in this case the apparent degree of crosslinking is smaller. Thus, vulcanization appears to enhance the contribution of rubber-particle bonding to the elastic modulus and restricted swelling of carbon-black-filled vulcanizates. Simple procedures are suggested for estimating the actual degree of crosslinking in filled rubber vulcanizates from measurements of equilibrium swelling or elastic modulus.
Like 1,4-bis(3-quinolyl)buta-1,3-diyne, its structural isomer, 1,4-bis(4-isquinolyl)buta-1,3-diyne, undergoes both photo-and thermal polymerization. Thermal polymerization of each material leads to more amorphous, less thermally stable polymers than are observed in the respective photopolymerization. The diacetylenes are found to react with certain organoiodines to give N-I charge-transfer complexes. Thermolysis of the complexes evolves the organoiodine species prior to polymerization of the diacetylene. The complexes fail to polymerize upon photolysis.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.