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Published on: July 10, 2016
Phase-dependent premelting of self-assembled phosphonic acid multilayers.
M de Pauli1, R Magalhães-Paniago, A Malachias
1Departamento de Física, Universidade Federal de Minas Gerais, Avenida Antonio Carlos 6627, Belo Horizonte-MG, CEP: 30123-970, Brazil.
Summary
Supramolecular assembly configuration, not molecule length, dictates premelting in phosphonic acids. Straight lamellar packing favors premelting, while tilted packing disfavors it, revealing configuration-dependent melting behaviors.
Area of Science:
- Materials Science
- Physical Chemistry
- Surface Science
Background:
- Melting and premelting phenomena in self-organized organic systems are well-studied.
- The impact of supramolecular assembly configuration on premelting is less understood.
- Phosphonic acids serve as model systems for ordered molecular assemblies on substrates.
Purpose of the Study:
- To investigate how supramolecular assembly configuration influences premelting in phosphonic acids.
- To explore the role of lamellar packing in the melting behavior of octadecyl and octyl phosphonic acids.
- To understand the relationship between molecular interactions and premelting phenomena.
Main Methods:
- Utilizing phosphonic acids as model systems for self-organized molecular assemblies.
- Investigating long-range order and distinct stacking types (lamellar structures) on various substrates.
- Comparing the premelting behavior of octadecyl phosphonic acid and octyl phosphonic acid.
Main Results:
- Premelting occurs in lamellar structures, with behavior directly dependent on the ordered configuration.
- Molecule length showed minimal influence on premelting; configuration was the dominant factor.
- Tilted packings unfavored premelting, whereas straight configurations exhibited strong premelting.
- Premelting initiated at domain boundaries in straight lamellar configurations.
- Observed power law temperature dependence for domain sizes.
Conclusions:
- The lamellar packing configuration critically controls premelting in phosphonic acid multilayers.
- Straight configurations, with weaker alkyl chain interactions, promote significant premelting.
- Understanding these configuration-dependent melting behaviors is crucial for designing self-organized organic systems.
