Programmed folding into spiro-multicyclic polymer topologies from linear and star-shaped chains

Abstract

The development of precise folding techniques for synthetic polymer chains that replicate the unique structures and functions of biopolymers has long been a key challenge. In particular, spiro-type (i.e., 8-, trefoil-, and quatrefoil-shaped) polymer topologies remain challenging due to their inherent structural complexity. Herein, we establish a folding strategy to produce spiro-type multicyclic polymers via intramolecular ring-opening metathesis oligomerization of the norbornenyl groups attached at predetermined positions along a synthetic polymer precursor. This strategy provides easy access to the desired spiro-type topological polymers with a controllable number of ring units and molecular weight while retaining narrow dispersity (Ɖ < 1.1). This effective strategy marks an advancement in the development of functionalized materials composed of specific three-dimensional nanostructures.

Topology Transformation toward Cyclic, Figure-Eight-Shaped, and Cross-Linked Polymers Based on the Dynamic Behavior of a Bis(hindered amino)disulfide Linker

“…The dynamic structure of the figure-eight-shaped polymer during the gelation process was characterized using dynamic light scattering under concentrated conditions of 200 g/L. The scattering intensity and the intensity correlation function (ICF), g (2) (τ) − 1, were collected as a function of the reaction time at 90 °C at a fixed scattering angle of 90°. Figure 4a shows the time-averaged scattering intensity at 30 s intervals.…”

“…36 As the cross-linking proceeds, the polymer clusters become larger, and their dynamics become slower. After the gel point, the initial value of the ICF, g (2) (0) − 1, gradually decreased, indicating the formation of a nonrelaxing polymer network in the gel. When the gel network was well formed (t > 60 min), the slow relaxation mode disappeared and only the fast mode persisted, showing that most of the polymer clusters were incorporated in the gel network and that the gel dynamics could be described purely by the cooperative diffusion of the polymer chains.…”

“…Analogues of cyclic polymers, such as figure-eightshaped polymers, cage-shaped polymers, and trefoil-shaped polymers, are mainly synthesized by a combination of a ringclosure strategy followed by polymer reactions, making their synthesis more elaborate. 2,30,31 Recently, we have developed a simple and efficient method toward cyclic topologies, macrocycles, and cyclic polymers using the dynamic nature of bis(2,2,6,6-tetramethylpiperidin-1yl)disulfide (BiTEMPS) (Figure 1a). 32 The cyclization of polymers with BiTEMPS moieties in their repeating units can be induced by simple dilution and heating; i.e., no catalysts and/or additives are required.…”

“…In polymer chemistry, the properties and functionalities of polymers are governed by their topologies (e.g., linear, cyclic, or branched). Accordingly, polymers with a variety of topologies have been synthesized and proven useful in a variety of applications. − Topology-transformable polymers have attracted considerable attention in recent decades because their primary structure can be changed, which in turn alters their properties. − Dynamic covalent chemistry (DCC) is a powerful tool to achieve the topology transformation of polymer chains, as it combines the dynamic nature of supramolecular chemistry with the strength of covalent bonds. , Hence, various types of topology transformations based on DCC have been reported. − However, topology transformations to produce cyclic topologies remain challenging due to the difficulties associated with precisely controlling the presence/absence of specific terminal structures in the products. Thus, it can be expected to be as challenging but interesting to achieve a DCC equilibrium without terminal structures.…”

“…However, highly dilute conditions are required to minimize the formation of linear polymeric byproducts generated via intermolecular reactions; the resulting inefficiency of this method prevents its scale-up. Analogues of cyclic polymers, such as figure-eight-shaped polymers, cage-shaped polymers, and trefoil-shaped polymers, are mainly synthesized by a combination of a ring-closure strategy followed by polymer reactions, making their synthesis more elaborate. ,, …”