Controlling Polymer Crystallization Kinetics by Sample History. Issue 3 (23rd August 2017)

• Record Type: Journal Article
• Authors: Poudel, Purushottam; Chandran, Sivasurender; Majumder, Sumit; Reiter, Günter
• Other Names: Unterlass Miriam M. guestEditor.; Ando Shinji guestEditor.; Tsui Ophelia K. C. guestEditor.
• Is Part Of: Macromolecular chemistry and physics. Volume 219:Issue 3(2018)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2017-08-23
• Subjects: crystallization kinetics -- nonequilibrium chain conformations -- polymer thin films -- quiescent conditions -- spin coating; Polymers -- Periodicals; Polymerization -- Periodicals; Synthetic products -- Periodicals; Macromolecules -- Periodicals; 547.7
• DOI: 10.1002/macp.201700315
• Languages: English
• ISSNs: 1022-1352

Abstract

Abstract: In this paper systematic changes in the isothermal crystallization kinetics (at T c = 200 °C) of nonequilibrated isotactic polystyrene films, generated through spin coating are reported. Kinetics is tuned by annealing films at T a = 250 °C, i.e., above their nominal melting temperature ( T m DSC = 220 °C). An exponential decrease in growth rate and a significant decrease of crystal nucleation density by approximately three orders of magnitude are observed by increasing the time ( t a ) provided for equilibration at T a . The characteristic exponential decay time is approximately four orders of magnitude longer than the equilibrium reptation time at T a . Interestingly, with increasing t a, a change in the morphology of lamellar crystals varying from spherulites to hexagons of rather uniform height to finally hexagons exhibiting periodic modulations in height is observed. These observations reveal that understanding and tuning the crystallization kinetics of polymer films under quiescent conditions requires knowledge on how strongly chain conformations deviate from equilibrium. Abstract : Tuned by annealing above the nominal melting temperature, isothermal crystallization kinetics of nonequilibrated isotactic polystyrene films changes systematically. Increasing the time provided for equilibration, crystal nucleation density and growth rate decrease exponentially at an extraodinary slow rate. Concurrently, the morphology changes from spherulites to hexagons of rather uniform height to finally hexagons exhibiting periodic modulations in height.