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The fundamental bases of liquid crystals and polymers–both widely employed in, and critically important to, modern society–apparently remain poorly understood. Hence, the need to explore alternative explanations to current paradigms.
Thus, liquid crystals are viewed as partially molten solids that retain a semblance of the order of their crystalline precursors. However, this seems unviable as the long-range order in the resulting mesophase cannot survive at temperatures higher than the melting point of the crystal itself.
In polymers, the non-covalent intermolecular forces are believed to be additively amplified along the length of the macromolecule. However, this ignores the fact that the said forces remain minuscule at the sub-unit level, so a collection of macromolecules would be continually associating and dissociating at each contact point. It is doubtful that this can explain the observed mechanical strength of polymers (leading to the “polythene enigma”).
It is argued herein that liquid crystals arise via the entanglement of long chains and U-shaped moieties in the incipient crystalline melt, a process essentially facilitated by proximity effects in the crystal. Thus, the entanglements are not easily reversed once the proximity effects are lost in the mesophase, which is likely a nanoparticle aggregate possibly composed of quasi-rotaxane and quasi-catenane species. Furthermore, liquid crystals–even those derived from achiral molecules–display optical activity, which is critical to their application in display devices. Although this symmetry breaking remains enigmatic, a chiral mechanochemical effect or even parity violation are possible explanations.
In the case of macromolecular association, it is argued that the van der Waals force is inherently strong in enthalpy terms, but is stymied by entropic effects which dominate in the weak forces (generally). However, the entropic effects are possibly “damped” in the macromolecule (although in a subtle manner), so association is much greater than currently estimated. These lead to interesting theoretical insights into enthalpy-entropy relationships in atomic and molecular interactions, a sigmoid relationship possibly being indicated.
Fahlman B. Materials chemistry. Dordrecht: Springer Netherlands; 2018.
Naumann RJ. Introduction to the physics and chemistry of materials. Boca Raton FL: CRC Press (Taylor & Francis Group); 2009.
Ariga K, Kunitake T. Supramolecular chemistry – Fundamentals and applications. Berlin-Heidelberg: Springer-Verlag; 2006.
Chandrasekhar S. Liquid-crystal structure and theory: The chimerical mesophase. Towards a new paradigm based on chiral symmetry breaking. viXra E-Print Archive; 2015. Available: viXra: 1503.0010. Accessed 2020.
Chandrasekhar S. Macromolecular aggregation, supramolecular stability and polymer strength: Has the van der Waals force been underestimated? viXra E-Print Archive; 2012. Available: viXra:1210.0102. Accessed 2020.
Geelhaar T, Griesar K, Reckmann B. 125 Years of liquid crystals—A scientific revolution in the home. Angew Chem Int Ed. 2013;52(34):8798-8809. DOI: 10.1002/anie.201301457
Bremer M, Kirsch P, Klasen-Memmer M, Tarumi K. The TV in your pocket: Development of liquid crystal materials for the new millennium. Angew Chem Int Ed. 2013;52(34):8880-8896. DOI: 10.1002/anie.201300903
Fleischmann E-K, Zentel R. Liquid-crystalline ordering as a concept in materials science: From semiconductors to stimuli-responsive devices. Angew Chem Int Ed. 2013;52(34):8810-8827. DOI: 10.1002/anie.201300371
Adrienko D. Introduction to liquid crystals. Journal of Molecular Liquids. 2018;267:520-541. DOI:https://doi.org/10.1016/j.molliq.2018.01
Tschierske C. Development of structural complexity by liquid-crystal self-assembly. Angew Chem Int Ed. 2013;52(34):8828-8878. DOI: 10.1002/anie.201300872
Uchida T. 40 years of research and development on liquid crystal displays. Jpn J Appl Phys. 2014;53:03CA02-(1-6). DOI:10.7567/JJAP.53.03CA02
Lagerwall JPF, Scalia G. A new era for liquid crystal research: Applications of liquid crystals in soft matter nano-, bio- and microtechnology. Curr Appl Phys. 2012; 12:1387-1412. DOI: 10.1016/j.cap.2012.03.019
Sohn JI, Hong W-K, Choi SS, Coles HJ, Welland ME, Cha SN, et al. Emerging applications of liquid crystals based on nanotechnology. Materials. 2014;7:2044-2061. DOI:10.3390/ma7032044
Sluysmans D, Stoddart JF. The burgeoning of mechanically interlocked molecules in chemistry. Trends in Chemistry. 2019;1(2):185-197. DOI: 10.1016/j.trechm.2019.02.013
Taghavi Shahraki BT, Maghsoudi S, Fatahi Y, Rabiee N, Bahadorikhalili S, Dinarvand R, et al. The flowering of mechanically interlocked molecules: Novel approaches to the synthesis of rotaxanes and catenanes. Coordination Chemistry Reviews. 2020;423:213484. DOI: doi.org/10.1016/j.ccr.2020.213484
Dierking I. Chiral liquid crystals: Structures, phases, effects. Symmetry. 2014;6:444-472. DOI:10.3390/sym6020444
Tschierske C, Dressel C. Mirror symmetry breaking in liquids and their impact on the development of homochirality in abiogenesis: Emerging proto-RNA as source of biochirality? Symmetry. 2020; 12:1098-1127. DOI:10.3390/sym12071098
Lewandowski W, Vaupotič N, Pociecha D, Górecka E, Liz-Marzán LM. Chirality of liquid crystals formed from achiral molecules revealed by resonant X-ray scattering. Adv Mater. 2020;32(41): 1905591. DOI: 10.1002/adma.201905591
Eliel EL, Wilen SH, Mander LN. Stereochemistry of organic compounds. New York: John Wiley; 1994.
Chandrasekhar S. Molecular homochirality and the parity violating energy difference. A critique with new proposals. Chirality 2008;20(2):84-95. DOI: doi.org/10.1002/chir.20502
Hota R. Novel studies in organic stereochemistry (PhD Thesis). Bangalore (India): Indian Institute of Science; 2006.
Traeger H, Kiebala DJ, Weder C, Schrettl S. From molecules to polymers—harnessing inter- and intramolecular interactions to create mechanochromic materials. Macromol Rapid Commun. 2020;2000573. DOI: 10.1002/marc.202000573
Nicholson JW. The chemistry of polymers. 3rd ed. Cambridge (UK): The Royal Society of Chemistry; 2006.
Mabesoone MFJ, Palmans ARA, Meijer EW. Solute-solvent interactions in modern physical organic chemistry: Supramolecular polymers as a muse. J Amer Chem Soc. 2020;142(47):19781-19798. DOI: 10.1021/jacs.0c09293
Atkins PW. Physical chemistry. 5th ed. Oxford: Oxford University Press; 1995.
Burger FA, Corkery, RW, Buhmann SY, Fiedler J. Comparison of theory and experiments on van der Waals forces in media—A survey. J Phys Chem (C). 2020; 14(44):24179–24186. DOI: 10.1021/acs.jpcc.0c06748
Lide DR, ed. CRC handbook of chemistry and physics. 85th ed. Boca Raton FL: CRC Press; 2004.
Ohkubo YZ, Thorpe IF. Evaluating the conformational entropy of macromolecules using an energy decomposition approach. J Chem Phys. 2006;124(2):024910. DOI: 10.1063/1.2138696