Self‐Assembly of Epoxy‐Based Polymers

Abstract

IntroductionAmphiphilic polymers have proved to be very versatile precursors for the synthesis of nanostructured systems by self -assembly. Dendrimers, polysoaps and block copolymers have been used successfully to obtain micelles, nanostructured fi lms and mesophases with different levels of organization [1 -3] . Hydrophobic interactions are important in the formation of many kinds of organized polymer aggregates and gels. We can fi nd good examples of the role of van der Waals interactions between long alkyl chains in the self -assembly of metal nanoparticles [4] , metal thiolates [5] , and organic -inorganic hybrid materials [6,7] .The way in which alkyl chains are usually associated can be illustrated by the self -assembly and polycondensation of alkylsilanetriols, C n H 2 n +1 Si(OH) 3 [7,8] . Figure 6.1 shows the crystalline -layered structure formed by these materials. The most characteristic feature is the tail -to -tail association of alkyl chains between siloxane layers. The X -ray spectra of the material with n = 18 shows a main peak at an angle corresponding to a characteristic distance of 5.3 nm [7] , equal to the length of two extended (all -trans) octadecyl chains. Higher -order refl ections up to the 12th order were recorded, that are characteristic of the lamellar order obtained by the tail -to -tail association of alkyl chains. At a higher angle, a broad peak with a maximum at a characteristic distance of 0.42 nm was also observed. This distance is close to the lateral interchain distance of closely packed alkyl chains (for the orthorhombic cell of polyethylene, the shortest interchain distance is 0.445 nm).The tail -to -tail association between alkyl chains and the high packing density of the generated hydrophobic domains seem to be a general characteristic of their self -assembly. However, all -trans conformations of alkyl chains are not always obtained. Depending on the particular system and processing conditions, transgauche conformations and interdigitation of alkyl chains can be observed. This produces a reduction of the characteristic distance of tail -to -tail associations (Figure 6.2 ). For example, under specifi c conditions gold nanoparticles coated with alkanethiol chains become self -assembled as colloidal crystals. In this case, the 6 Epoxy Polymers. Edited

Shape memory epoxies based on networks with chemical and physical crosslinks

“…An example of such an epoxy is the one synthesized by the reaction of diglycidylether of bisphenol A (DGEBA) with an n-alkylamine. These linear polymers form strong physical crosslinks by tail-to-tail associations among alkyl chains and exhibit the behavior of a physical network [24][25][26]. As an example, Fig.…”

Recent Advances in UV-Cured Encapsulation for Stable and Durable Perovskite Solar Cell Devices

“…Once epoxy resin undergoes 3D network crosslinking, it exhibits high adhesive strength. The epoxy groups and hydroxyl groups on the glass surface readily engage in intermolecular interactions and hydrogen bonding [75]. This ability allows the resin to firmly bond with the PSCs and other encapsulation materials, thereby strengthening the robustness of the encapsulation layer [75].…”

“…The epoxy groups and hydroxyl groups on the glass surface readily engage in intermolecular interactions and hydrogen bonding [75]. This ability allows the resin to firmly bond with the PSCs and other encapsulation materials, thereby strengthening the robustness of the encapsulation layer [75]. UV-curable resins also have low shrinkage properties, which ensures a low risk of detaching from the PSC or any other encapsulation materials during the curing process, giving a more uniform and solid encapsulation layer [76].…”