Odd–even alternations in helical propensity of a homologous series of hydrocarbons

Pradeilles, Johan A.; Zhong, Siying; Baglyas, Márton; Tarczay, György; Butts, Craig P.; Myers, Eddie L.; Aggarwal, Varinder K.

doi:10.1038/s41557-020-0429-0

Cited by 37 publications

(28 citation statements)

References 29 publications

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“…93 However, this explanation does not apply to isolated polymer chains, which do not exhibit any crystalline aggregates. An alternative mechanism, which has been demonstrated for alkyl chains in solution, links the odd/effect to alkyl chain conformations and their population, 94,95 in alignment with our observations that isolated odd and even CBS-m polymer chains have different sizes of the conformational space they can populate.…”

Section: Isolated Chain Dynamicssupporting

confidence: 88%

Thermomechanical enhancement of DPP‐4T through purposeful π‐conjugation disruption

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et al. 2021

Journal of Polymer Science

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The design of polymer-based organic semiconductors that offer mechanical deformability while maintaining efficient semiconducting characteristics remains a significant challenge. Recent synthetic efforts have incorporated small alkyl segments directly into otherwise π-conjugated polymer backbones to enhance processability, mechanical deformability, and other properties. The resulting polymers can be used as stand-alone materials or as matrix polymers in complementary semiconducting polymer blends offering reasonable chargecarrier transport properties, thermal healing, and deformability. Here, a family of diketopyrrolopyrrole-tetrathiophene variants is explored via large-scale atomistic molecular dynamics simulations to examine the effect of alkyl segments incorporated into the polymer backbone on the polymer structure, dynamics, and thermal properties. Longer alkyl segments lead to polymer chains that are more flexible, compact, and mobile, with lower glass transition temperatures for the condensed phase.

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Section: Isolated Chain Dynamicssupporting

confidence: 88%

Thermomechanical enhancement of DPP‐4T through purposeful π‐conjugation disruption

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et al. 2021

Journal of Polymer Science

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“…Parity effects in solid condensed phases often arise from differences in the intermolecular interactions and molecular packing. A classic example is the odd–even variation of the melting points of solids of odd- and even-numbered n -alkanes and n -alkyl carboxylic acids. , SAM properties exhibiting parity effects include surface wettability, friction, and electron transfer rate . Charge tunneling across metal–SAM–metal junctions is particularly sensitive to the SAM structure.…”

Section: Introductionmentioning

confidence: 99%

Molecular Origin of the Odd–Even Effect of Macroscopic Properties of n-Alkanethiolate Self-Assembled Monolayers: Bulk or Interface?

et al. 2020

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Elucidating the influence of the monolayer interface versus bulk on the macroscopic properties (e.g., surface hydrophobicity, charge transport, and electron transfer) of organic self-assembled monolayers (SAMs) chemically anchored to metal surfaces is a challenge. This article reports the characterization of prototypical SAMs of n-alkanethiolates on gold (CH3(CH2)nSAu, n = 6-19) at the macroscopic scale by electrochemical impedance spectroscopy and contact angle goniometry, and at the molecular level, by infrared reflection absorption spectroscopy. The SAM capacitance, dielectric constant, and surface hydrophobicity exhibit dependencies on both the length (n) and parity (nodd or neven) of the polymethylene chain. The peak positions of the CH2 stretching modes indicate a progressive increase in the chain conformational order with increasing n between n = 6 and 16. SAMs of nodd have a greater degree of structural gauche defects than SAMs of neven. The peak intensities and positions of the CH3 stretching modes are chain length independent but show an odd-even alternation of the spatial orientation of the terminal CH3. The correlations between the different data trends establish that the chain length dependencies of the dielectric constant and surface hydrophobicity originate from changes in the polymethylene chain conformation (bulk), while the odd-even variation arises primarily from a difference in the chemical composition of the interface related to the terminal group orientation. These findings provide new physical insights into the structure-property relation of SAMs for the design of ultrathin film dielectrics as well as the understanding of stereostructural effects on the electrical characteristics of tunnel junctions.

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“…Several studies reported that the odd−even sidechain length of n-alkyl-substituted homologues significantly affects their packing configuration and consequently alters the water affinity. 33,34 We speculate that a similar odd−even effect might account for the water content changes along with Cn in our Cn-0.5 series. Explicit explanation of such a relationship between water content and odd−even alkyl chain length is a complex task and remains an interesting subject for future exploration.…”

Section: Resultsmentioning

confidence: 65%

Length Effects of Short Alkyl Side Chains on Phase-Separated Structure and Dynamics of Hydrophobic Association Hydrogels

et al. 2021

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Phase separation plays a crucial role in toughening hydrogels. Thus, regulating the phase-separation structure is vital to understanding the toughening mechanism in phase-separated hydrogels. Current synthesis strategies often provide limited control on phase-separated structures. In this work, a library of short-alkyl-side-chain-modified hydrogels is fabricated as model phase-separated hydrogels to investigate the length effects of short alkyl side chains on the phase-separated structure, apparent mechanics, and dynamics. Short-alkyl-chain-modified polymers undergo vapor-induced phase separation from highly concentrated solutions and coalesce into a well-connected polymer-rich phase. With increasing length of the side chains, the polymer-rich domain thickens due to enhanced hydrophobic interaction. Rheology suggests that longer alkyl side chains result in higher “glass”-transition temperatures and slower dynamics. However, by correlating the stretch rate and temperature dependence of both the small deformation properties (linear rheology) and the large deformation properties (tensile behavior), we find that regardless of the length of the side chain, hydrogels become tough and strong when the tensile test temperature approaches the glass-transition temperature or the stretch rate matches the relaxation time in the intermediate frequency regime. The strength and toughness of the gels obtained in this work are the combined effect of phase separation and glass transition. This work sheds light on the design principles for the mechanical elements in phase-separated hydrogels.

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Odd–even alternations in helical propensity of a homologous series of hydrocarbons

Cited by 37 publications

References 29 publications

Thermomechanical enhancement of DPP‐4T through purposeful π‐conjugation disruption

Thermomechanical enhancement of DPP‐4T through purposeful π‐conjugation disruption

Molecular Origin of the Odd–Even Effect of Macroscopic Properties of n-Alkanethiolate Self-Assembled Monolayers: Bulk or Interface?

Length Effects of Short Alkyl Side Chains on Phase-Separated Structure and Dynamics of Hydrophobic Association Hydrogels

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