Some thoughts about controllable assembly (I) — From catalysis to cassemblysis

Abstract

Molecular assembly processes are in general much more complex than chemical synthesis. Their goal is the same, that to create a variety of new matter and new functional materials. In accordance with their similarities, the concept of catalysis, which is widely used in chemical synthesis, could be extended to assembly. Herein we suggest that the term “cassemblysis” be used when referring to increased rates and control during assembly. The role played by a cassemblyst in molecular assembly is similar to that played by a catalyst in a synthesis with high efficiency and selectivity. Furthermore, it may be helpful to classify some terms which are used often but without clarity in the literature, such as self-assembly and assisted self-assembly. Molecular assembly can be divided into two major types, self-assembly and assisted assembly. Most assembly processes belong to assisted assembly, which can be further divided into three categories: cassemblysis, co-assembly and field-assisted assembly. Of these three, cassemblysis is the most efficient way to create new materials (e.g., soft matter) above the molecular level. After cassemblysis, some assembly systems undergo a chemical coupling reaction which significantly enhances stability and prevents them from de-assembling. This increased stability is essential for practical applications. We call this cassembly-reaction process “catassemblysis”. We present some typical examples involving small molecules and large biological molecules to show that cassemblysis and catassemblysis are very common, especially in biological systems. We believe that photo-electro-cassemblysis is possible and that the concept of cassembly could be extended to controllable nanoparticle (or other nanostructure) assembly. Finally we discuss the primary mechanism of cassemblysis and catassemblysis. With emphasis on the experimental and theoretical methodologies of cassemblysis, controllable assembly could play a greater role in creating new matter and new functional materials.