Supramolecular polymers

30. quasi-block copolymers

Supramolecular polymers are environmentally responsive. Block copolymers are nano-structured. What happens if you join both principles? You get a quasi-block copolymer, which should be both structured and dynamic.

Below you can find our initial papers that explore this concept both experimentally and by simulation.

Columbus, I. ; Eren, N. ; Elitsur, R. ; Davidovich-Pinhas, M. ; Shenhar, R. Branched Supramolecular Copolymers: Inducing Branching in Bisurea-Based Monomers Using Multi-Sulfonate Molecules. Macromolecules 2022, 55, 472–487. DOIAbstract

Supramolecular polymers are based on noncovalent interactions, which impart unique properties such as dynamic behavior, concentration-dependent degree of polymerization, and environmental responsiveness. While linear supramolecular polymers are ubiquitous and have been extensively studied, branched polymers that are based exclusively on supramolecular interactions are much less abundant, and a fundamental understanding of their molecular-level structure is still lacking. We report on the preparation of branched, all-supramolecular polymers based on a combination of a bisureidotoluene building block [N,N′-2,4-bis((2-ethylhexyl)ureido)toluene (EHUT)], which is associated with four-point hydrogen bonding, and three anionic co-monomers featuring one, two, or three sulfonate groups. The co-monomers were designed to serve as a chain stopper, a bifunctional linear comonomer, and a branch point. Whereas combination of EHUT with the singly functionalized co-monomer led to linear supramolecular chains, diffusion and viscosity data indicate that branched supramolecular polymers were obtained when EHUT was combined not only with the triply functionalized molecules but also with the doubly functionalized molecules. Theoretical analysis based on an adaptation of Flory’s theory of branched polymers suggests that in both cases, the interaction of certain EHUT units
with the multiply functionalized co-monomers converted these EHUT units into branch points, which led to substantially reduced viscosities in these systems. The insights gained from this study enable tuning the properties of supramolecular polymers not only by
concentration and temperature but also by introducing appropriately designed molecular additives. This may lead to the development of sophisticated smart materials.

Sanguramath, R. A. ; Nealey, P. F. ; Shenhar, R. Quasi-Block Copolymers Based on a General Polymeric Chain Stopper. Chemistry-A European Journal 2016, 22, 10203-10210.Abstract

Quasi-block copolymers (q-BCPs) are block copolymers consisting of conventional and supramolecular blocks, in which the conventional block is end-terminated by a functionality that interacts with the supramolecular monomer (a ``chain stopper'' functionality). A new design of q-BCPs based on a general polymeric chain stopper, which consists of polystyrene end-terminated with a sulfonate group (PS-SO3Li), is described. Through viscosity measurements and a detailed diffusion-ordered NMR spectroscopy study, it is shown that PS-SO3Li can effectively cap two types of model supramolecular monomers to form q-BCPs in solution. Furthermore, differential scanning calorimetry data and structural characterization of thin films by scanning force microscopy suggests the existence of the q-BCP architecture in the melt. The new design considerably simplifies the synthesis of polymeric chain stoppers; thus promoting the utilization of q-BCPs as smart, nanostructured materials.

46. universal quasi-block copolymers

Weiss, E. ; Daoulas, K. C. ; Mueller, M. ; Shenhar, R. Quasi-Block Copolymers: Design, Synthesis, and Evidence for Their Formation in Solution and in the Melt. Macromolecules 2011, 44, 9773-9781.Abstract

A family of block copolymers featuring dynamically controlled compositions is presented. These copolymers, termed ``quasi-block copolymers'' (q-BCP), consist of a supramolecular polymer as one of the blocks. A conventional polymer end-capped with a functionality that is complementary to the supramolecular monomer is used to terminate the supramolecular block, giving rise to a block copolymer architecture. In this work we have utilized N,N'-2,4-bis((2-ethylhexyl)ureido)toluene (EHUT) as the supramolecular monomer and employed two types of modified 2,4-bis(ureido)toluene polystyrenes as the end-functionalized conventional polymer. Solution viscosity measurements with different solvent compositions and DSC analysis of poly(EHUT)/functionalized-PS blends provide compelling evidence for the formation of self-assembled q-BCP structures both in solution and in the melt. The qualitative role of chain stoppers on the molecular weight distribution is studied by simulations.

30. quasi-block copolymers

Daoulas, K. C. ; Cavallo, A. ; Shenhar, R. ; Mueller, M. Directed Assembly of Supramolecular Copolymers in Thin Films: Thermodynamic and Kinetic Advantages. Physical Review Letters 2010, 105, 108301.Abstract

Using computer simulation of a coarse-grained model for supramolecular polymers, we investigate the potential of quasiblock copolymers (QBCPs) assembled on chemically patterned substrates for creating device-oriented nanostructures. QBCPs are comprised of AB diblock copolymers and supramolecular B segments that can reversibly bond to any available B terminus, on either the copolymers or the B oligomers, creating a polydisperse blend of B homopolymers, and AB and ABA copolymers. We demonstrate the defect-free replication of patterns with perpendicularly crossing, A-preferential lines, where the same QBCP can simultaneously replicate patterns differing by up to 50% in their length scales. We demonstrate how the pattern affects the distribution of molecular architectures and the key role of supramolecular associations for replicating patterns with different length scales.

26. quasi-block copolymer on patterns - theory

Daoulas, K. C. ; Cavallo, A. ; Shenhar, R. ; Mueller, M. Phase behaviour of quasi-block copolymers: A DFT-based Monte-Carlo study. Soft Matter 2009, 5 4499-4509.Abstract

We develop a mesoscopic density functional theory (DFT)-based Monte-Carlo approach for studying the phase behaviour of multi-component systems comprised of irreversibly bonded, conventional macromolecules and supramolecular entities. The latter can reversibly associate with each other and the conventional components to ``living'', equilibrium polymers. The computational approach can be applied to a broad class of supramolecular systems and we focus here on quasi-block copolymer systems that contain conventional, ``dead'' AB-copolymers with a supramolecular B-terminus and supramolecular B-units. The simulations show that, by properly selecting the architecture of the ``dead'' copolymers and by varying the supramolecular association constant and the incompatibility between the segment species, A and B, one obtains a variety of different microphase-separated morphologies and macrophase separations. Two representative phase diagrams are reported as a function of the association constant, E(b), and the Flory-Huggins parameter, chi, quantifying the repulsion between A and B segments. The simulation results are qualitatively rationalised by considering the dependence of the stoichiometry on the system's parameters, and fractionation effects between coexisting phases are illustrated.

19. quasi-block copolymer theory