Yang P, Han Y. Crystal growth transition from flat-on to edge-on induced by solvent evaporation in ultrathin films of polystyrene-b-poly(ethylene oxide).
LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009;
25:9960-9968. [PMID:
19705892 DOI:
10.1021/la901108p]
[Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The transition of lamellar crystal orientation from flat-on to edge-on in ultrathin films of polystyrene-b-poly(ethylene oxide) (PS-b-PEO) via solvent vapor (toluene) treatment was investigated. When the as-prepared film was treated in saturated solvent vapor, breakout crystals could form quickly, and then they transformed from square single crystals (flat-on lamellae) to dendrites and finally to nanowire crystals (edge-on lamellae). Initially, heterogeneous nucleation at the polymer/substrate interface dominated the structure evolution, leading to flat-on lamellar crystals orientation. And the transition from faceted habits to dendrites indicated a transition of underlying mechanism from nucleation-controlled to diffusion-limited growth. As the solvent molecules gradually diffused into the polymer/substrate interface, it will subsequently weaken the polymer-substrate interaction. In this case, lower free energy lamellae of an edge-on orientation could be obtained by the gain of free volume of the soluble PS block.
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