Shape Persistence in Polymers and Supramolecular Assemblies

Abstract

A thorough insight into the shape of polymers and supramolecular assemblies is of crucial importance for the flow behavior, the packing in the solid as well as the structure and dynamics in non-dilute solutions. In this chapter, we present the main experimental techniques that can reliably address persistence and compare different polymers with reported persistence lengths ranging from few nanometers to few hundreds nanometers. Specifically, we discuss not only the so-called rigid-rod polymers such as polyphenylenes, but also dendronized and helical polymers. These chaintype macromolecules are generally considered as rigid or semi-rigid compared with conventional homopolymers such as polyolefins. Next it is meaningful to compare these covalently bonded polymers with supramolecular assemblies consisting of amphiphilic polymers such as poly(ethylene glycol) functionalized benzene derivatives and poly(ethylene oxide-b-butadiene). Supramolecular assemblies can assume larger rigidity than covalently bonded polymers. Although we can classify different types of polymers and supramolecular assemblies and determine their persistence lengths, so far, there is no clear structure-rigidity relationship. Hence, a prediction of the persistence lengths solely based on the molecular structures remains uncertain.

Rigidification of Poly(p-phenylene)s through ortho-Phenyl Substitution

“…Consistently, the fast diffusion coefficient, D = Γ( q )/ q 2 of the PPP 2 , is virtually q -independent (upper inset to Figure 3 ) due to the absence of internal dynamics contribution at high q ’s. 1 …”

“…Hence for short chains, information on the polymer conformation can only be extracted from the chain translational diffusion coefficient. Access to the rotational chain diffusion coefficient 1 is usually not feasible due to extremely low depolarized light scattering in very dilute solutions without an additional resonance-based enhancement. 35 …”

“…The chain stiffness of polymers is characterized by the persistence length, which is a measure of the chain rigidity and allows for a clear distinction between flexible and rigid-rod polymers. 1 It can be understood as the distance over which the orientation of the bonds persists. Rigid-rod polymers with high stiffness, such as poly( p -phenylene terephthalamide) (PPTA, Kevlar) 2 , 3 and poly( p -phenylene benzobioxazole) (PBO) 4 with persistence lengths of ∼20–50 nm, are used to prepare robust high-performance polymeric fibers, for a variety of applications including protective clothing and aerospace materials.…”

“…The chain stiffness of polymers is characterized by the persistence length, which is a measure of the chain rigidity and allows for a clear distinction between flexible and rigid-rod polymers . It can be understood as the distance over which the orientation of the bonds persists.…”

Conformation of Tunable Nanocylinders: Up to Sixth-Generation Dendronized Polymers via Graft-Through Approach by ROMP

“…4 One of the most interesting features of denpols, distinct from conventional linear polymers, is their extended or persistent conformation due to large steric repulsion among the side chains. 5,6 Hence, denpols possess rich perspectives for applications including drug delivery, 7 surface coating, 8 photonic crystals, 9 and molecular assemblies. 10 However, to what extent the polymer chains extend is often overlooked in most applications, 7−10 although chemists would agree that the denpols could transform from Gaussian coil to rod-like structures by increasing the generation of the dendron.…”