Quasi-block copolymers

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.

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.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