Collapse Transition‐Assisted Crystallization in P3HT Solution

Abstract

Understanding the multiple phase transitions such as collapse transition, phase separation, and crystallization in solutions is of fundamental importance to control the solution structure of conjugated polymers in device processing. Combining in situ synchrotron radiation small and wide‐angle X‐ray scattering, ultrasensitive differential scanning calorimetry, ultraviolet–visible absorption spectroscopy, and polarized optical microscopy, we investigate the order–disorder transitions in poly(3‐hexylthiophene)/toluene solutions during cooling and heating processes. We demonstrate the occurrence of collapse transition of polymer chains from a random coil state to a lower dimensional network prior to the onset of crystallization during cooling in solution. This conformational preordering can lead to the formation of a lyotropic liquid crystalline phase, which is of great significance to the crystallization and ordering in polymer films, and further to promote its electric performance. It is examined that the mobility of films cast from chain‐collapsed solutions can be one order of magnitude higher than that from isotropic solutions with random‐coiled conformations. Thus, the conformational preordering in solutions is proposed to be a more efficient way than the postannealing of films to improve the electric performance of conjugated polymer films. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1105–1114

Spark Discharge Doping—Achieving Unprecedented Control over Aggregate Fraction and Backbone Ordering in Poly(3‐hexylthiophene) Solutions

“…Temperature-induced disorder-order transitions in semiconducting polymers are widely studied. [20,37,[40][41][42][43][44][45] When the temperature of a polymer solution is decreased, the solvent quality decreases, and thus the polymer's solubility decreases accordingly. Upon reducing the temperature, P3HT undergoes a disorder-order transition from a random coil via a planarized coil and a disordered aggregate to a planarized aggregate and possibly a crystallized aggregate.…”

“…[20,37] Other parameters, such as, for example, poor solvent content and polymer concentration, can have a similar effect, and also other polymers undergo similar disorder-order transitions. [7,[10][11][12]20,[40][41][42][43][44][45][46] In the following, we will refer to the parameters influencing the solubility, like the polymer concentration, poor solvent concentration, and temperature as solubility parameters.…”

Recent progress in flow‐induced polymer crystallization

“…Recently, the crystallization behavior of highperformance thermoplastics under flow has attracted great attention. Here we taking poly(3-hexylthiophene)/ toluene (P3HT), [199][200][201] an organic optoelectronic material, and polyether ether ketone (PEEK), 101,102,[202][203][204] a hightemperature resistant and tough material, as examples. Sun et al 199 used in situ SR-SAXS/WAXS, DSC, ultraviolet-visible absorption spectroscopy and polarized optical microscopy to study the ordered-disordered transition of P3HT solutions under cooling and heating processes.…”

“…Here we taking poly(3-hexylthiophene)/ toluene (P3HT), [199][200][201] an organic optoelectronic material, and polyether ether ketone (PEEK), 101,102,[202][203][204] a hightemperature resistant and tough material, as examples. Sun et al 199 used in situ SR-SAXS/WAXS, DSC, ultraviolet-visible absorption spectroscopy and polarized optical microscopy to study the ordered-disordered transition of P3HT solutions under cooling and heating processes. It has been proved that during the cooling process, the polymer chain undergoes a collapse transformation from random coil state to low-dimensional network prior to the onset of crystallization.…”