Supramolecular Structures of Low-Molecular-Weight Polybutadienes, as Studied by Dynamic Light Scattering, NMR and Infrared Spectroscopy

Abstract

Three types of low-molecular-weight polybutadienes (bearing no or primary or secondary hydroxy groups on both chain ends), as well as their hydrogenated analogues, were studied by 1H NMR and IR spectroscopies and by dynamic light scattering. In bulk and at room temperature, hydroxylated polymers form hydrophilic microdomains (knots) based on hydrogen bonds between two or more OH end groups; these knots gradually disintegrate with increasing temperature and above 100 °C, only OH/OH pairs can be present, as is seen from IR spectra. Fixation of more than two chain ends in a single knot leads to the spatial restriction of the segmental motion of the chain links which manifests itself by the broadening of 1H NMR bands. With unsaturated, hydroxylated polymers, an intramolecular interaction between an OH end group and the adjacent CC bond of the terminal monomer unit is possible which makes the formation of the intermolecular OH/OH bonding less probable. The dynamic light scattering method revealed the presence of large clusters in bulk; these supramolecular structures are bound together not only by hydrogen bonds but also by interactions between the aliphatic chains. With increasing temperature, intermolecular hydrophobic domains dissociate only for unsaturated polymers.

Molecular Approach to Supramolecular Polymer Assembly by Small Angle Neutron Scattering

“…It is controlled by the Flory–Huggins χ parameter. This microphase segregation phenomenon can manifest itself either as a disordered clustering of the stickers ,− or as an ordered microphase separation as observed for block copolymers. − …”

“…It is also well-known that in many of these systems, microphase segregation between the spacer and the stickers, may occur, due to the different chemical composition, e.g polar stickers connected to an apolar spacer oligomer. − The compatibility between both is typically very low but can be enhanced by the ability of the stickers to form hydrogen bonds. It is controlled by the Flory–Huggins χ parameter.…”

Order–Disorder Transition in Supramolecular Polymers

“…The self-complementary binding stickers (A) are often hydrogen bonding motifs such as nucleobases or ureidopyrimidinone, while the spacer is generally an oligomer . In these systems, microphase segregation between the spacer and the stickers, − as well as crystallization of the stickers into microdomains , can occur. Indeed, hydrogen bonding motifs are usually more polar than the spacer and are prone to crystallization.…”

Energy of adsorption interaction and surface coverage from polymer of various molecular structures

“…In Ref. [24] while investigating the solutions of polybutadienes by means of dynamic light scattering, NMR, and IR spectroscopy it was found a presence of large quantity of clusters which are bound with each other not only due to hydrogen bonding, as in the case of butadienes with the end hydroxyl groups, but also due to the interaction between aliphatic chains, as in a case of polybutadiens without end hydroxyl groups. In the investigated solutions PB-CH 2 Cl 2 the polymer-polymer interaction dominates over the polymer-solvent interaction, consequently it is possible to assume that, as well as in Ref.…”

“…[24], macromolecules of PB form the macromolecular ensembles or clusters in these solutions even in a region C < C * . With the growth of concentration up to C = C * , increase of size and amount of clusters can results in formation of physical net of entanglements, which limits the segmental mobility of polymers, that is confirmed experimentally by the broadening of the band in the IR spectrum of PB with growth of concentration [24] and finally results in the diminishing of adsorption.…”