Phase Behavior of Amorphous/Semicrystalline Conjugated Polymer Blends

Abstract

We report the phase behavior of amorphous/semicrystalline conjugated polymer blends composed of low bandgap poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-b′]dithiophene) -alt-4,7(2,1,3-benzothiadiazole)] (PCPDTBT) and poly{(N,N′-bis(2-octyldodecyl)naphthalene -1,4,5,8-bis(dicarboximide)-2,6-diyl)-alt-5,5′-(2,2′-bithiophene)} (P(NDI2OD-T2)). As usual in polymer blends, these two polymers are immiscible because ΔSm ≈ 0 and ΔHm > 0, leading to ΔGm > 0, in which ΔSm, ΔHm, and ΔGm are the entropy, enthalpy, and Gibbs free energy of mixing, respectively. Specifically, the Flory–Huggins interaction parameter (χ) for the PCPDTBT /P(NDI2OD-T2) blend was estimated to be 1.26 at 298.15 K, indicating that the blend was immiscible. When thermally analyzed, the melting and crystallization point depression was observed with increasing PCPDTBT amounts in the blends. In the same vein, the X-ray diffraction (XRD) patterns showed that the π-π interactions in P(NDI2OD-T2) lamellae were diminished if PCPDTBT was incorporated into the blends. Finally, the correlation of the solid-liquid phase transition and structural information for the blend system may provide insight for understanding other amorphous/semicrystalline conjugated polymers used as active layers in all-polymer solar cells, although the specific morphology of a film is largely affected by nonequilibrium kinetics.

Molecular Compatibility and Hydrogen Bonding Mechanism of PES/PEI Blends

“…If the Gibbs free energy of the polymer blend casting solution system is less than 0, the two substances are compatible, according to the Flory–Huggins theory. As the entropy of blending of the polymer approaches zero, the Gibbs free energy of the blending system (Equation (6)) is mostly influenced by blending enthalpy [ 38 ]. As a result, Schneier et al deduced the formula for estimating the polymer blend system’s mixing enthalpy (Equation (7)) and determined that the mixing enthalpy’s critical value was 41.86 × 10 −3 J/mol [ 39 ].…”

Unrevealing the interaction between O2 molecules and poly(3-hexylthiophene-2,5-diyl) (P3HT)

“…It is known that conjugated polymers form amorphous and semicrystalline structures when processed to thin lms. [43][44][45] In the ordered regions the charge transport is delocalised whereas it is very localised in the amorphous parts. Thin lm crystallinity is determined by several parameters and depends on many conditions from synthesis to lm processing.…”

Self-Aligned Bilayers for Flexible Free-Standing Organic Field-Effect Transistors

“… 28 Both factors are controlled by a proper choice of components, blending ratio, and processing conditions to adjust favorable phase separation with the desired blend morphology. 29 One important factor among others is the molecular weight ( M w ) of the insulating polymer. The entropy of mixing is decreased and Δ G m is increased for high- M w insulators.…”

“…But so far, such binary blends have been mainly applied to improve the semiconductor morphology. − The phase separation of the two components is determined by the change of Gibbs free energy of mixing (Δ G m ) and the interaction parameter χ from the Flory–Huggins theory . Both factors are controlled by a proper choice of components, blending ratio, and processing conditions to adjust favorable phase separation with the desired blend morphology . One important factor among others is the molecular weight ( M w ) of the insulating polymer.…”