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A series of poly(amic acid)s have been synthesized from cyclobutane‐1,2,3,4‐tetracarboxylic dianhydride (CBDA), a functional diamine, 1‐(3,5‐diaminophenyl)‐3‐(1‐octadecyl)‐succinicimide and 4,4‐diaminodiphenylmethane (DDM) to give liquid crystal alignment layers with high pretilt angle after a rubbing process for vertically aligned liquid crystal display devices. Inherent viscosities of the poly(amic acid)s measured were in the range 0.2–1.56 dl/g, which decreased with an increase of content of 1‐(3,5‐diaminophenyl)‐3‐(1‐octadecyl)‐succinicimide. The cured polyimide films had good transparency, which was above 95% at 400 nm. Surface energies of all the polyimide films prepared from 1‐(3,5‐diaminophenyl)‐3‐(1‐octadecyl)‐succinicimide were below 40.7 dyn/cm before the rubbing process, which resulted in very high pretilt angles above 89°. By a rubbing process, the surface energy of the polyimide prepared from diamine mixture with 10 mol% of 1‐(3,5‐diaminophenyl)‐3‐(1‐octadecyl)‐succinicimide and 90% of DDM increased from 40.7 to 42.7 dyn/cm. Copyright © 2007 John Wiley & Sons, Ltd.

The aggregation behavior of polymers plays a crucial role in determining the optical, electrical, and morphological properties of donor−acceptor blends in both all-polymer solar cells (all-PSCs) and non-fullerene small-molecule acceptor− polymer solar cells (NFSMA−PSCs). However, direct comparison of the impacts on two different systems has not been reported, although it is important to design universal polymer donors (P D 's). Herein, three P D 's with different side chains (P−EH, P−SEH, and P−Si) are designed to study the P D aggregation effects on the blend morphology and device performance of both all-PSCs and NFSMA−PSCs. It is observed that the aggregation property of P D 's is a critical factor in determining the optimal blend morphologies and ultimately the device performances in both PSC systems. Furthermore, P D aggregation effects on device performance are significantly more impactful in all-PSCs than in NFSMA−PSCs. The P−Si P D exhibiting the strongest aggregation behavior in a processing solvent produces the most severe phase separation in the blend with a polymer acceptor, resulting in the lowest power conversion efficiency (PCE) of all-PSCs. In contrast, when P−Si is used in an NFSMA−PSC, a well-mixed blend morphology is observed, which results in the highest PCE of over 12%. These different roles dependent on P D aggregation mainly originate from the difference in molecular size of the polymer acceptor and small-molecule acceptor, which influences the entropic contribution to the formation of blend morphology. Our work provides a comprehensive understanding of the P D aggregation− blend morphology relationship in different all-PSC and NFSMA−PSC systems, which serves as an important guideline for the design of universal P D 's for both all-PSCs and NFSMA−PSCs.