Micellization Behaviour of Linear and Nonlinear Block Copolymers Based on Poly(n-hexyl isocyanate) in Selective Solvents.

Aggelos Vazaios,Georgia Zorba,Marinos Pitsikalis,Mikel Echeverria,Athanasios Touris

doi:10.3390/polym12081678

Aggelos Vazaios, Georgia Zorba + Show 3 more

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https://doi.org/10.3390/polym12081678

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Journal: Polymers	Publication Date: Jul 28, 2020
Citations: 5	License type: CC BY 4.0

Affiliation: National and Kapodistrian University of Athens

Abstract

Block copolymers have attracted significant scientific and economic interest over the last decades due to their ability to self-assemble into ordered structures both in bulk and in selective solvents. In this work, the self-assembly behaviour of both linear (diblocks, triblocks and pentablocks) and nonlinear (miktoarm stars and a block-graft) copolymers based on poly(n-hexyl isocyanate), PHIC, were studied in selective solvents such as n-heptane and n-dodecane. A variety of experimental techniques, namely static and dynamic light scattering, dilute solution viscometry and atomic force microscopy, were employed to study the micellar structural parameters (e.g., aggregation number, overall micellar size and shape, and core and shell dimensions). The effect of the macromolecular architecture, the molecular weight and the copolymer composition on the self-assembly behaviour was studied. Spherical micelles in equilibrium with clusters were obtained from the block copolymers. Thermally stable, uniform and spherical aggregates were found from the triblock copolymers. The poly(n-hexyl isocyanate)-b-polyisoprene-b-poly(n-hexyl isocyanate),-HIH copolymers tend to adopt closed loop conformation, leading to more elongated cylindrical-type structures upon increasing the concentration. Clustering effects were also reported in the case of the pentablock terpolymers. The topology of the blocks plays an important role, since the poly(n-hexyl isocyanate)-b-polystyrene-b-polyisoprene-b-polystyrene-b-poly(n-hexyl isocyanate), HSISH terpolymer shows intermicellar fusion of spherical micelles, leading to the formation of extended networks. The formation of spherical micelles in equilibrium with clusters was obvious in the case of the miktoarm stars, whereas the block-graft copolymer shows the existence of mainly unimolecular micelles.

Highlights

Block copolymers are without any doubt the most important class of polymeric materials [1,2].This is due (a) to the numerous methodologies and techniques that are available for the synthesis of well-defined products with predetermined molecular characteristics and low molecular and chemical heterogeneity
The samples are symbolized as SH followed by numbers denoting the sample’s molecular weight, the % wt content is PS and the % wt content in PHIC
The micellar solutions were obtained in n-heptane, which is a selective solvent for the PHIC block

Summary

Introduction

Block copolymers are without any doubt the most important class of polymeric materials [1,2].This is due (a) to the numerous methodologies and techniques that are available for the synthesis of well-defined products with predetermined molecular characteristics and low molecular and chemical heterogeneity. Polymers 2020, 12, 1678 solvent, which is a thermodynamically good solvent for the one block and non-solvent for the other block, the copolymers self-assemble, leading to the formation of supramolecular structures, called for the one block non-solvent for theand other block,applications, the copolymers leading to micelles [7,8,9], andand (c) to their numerous diverse such self-assemble, as colloidal stabilization the formation of supramolecular structures, called micelles [7,8,9], and (c) to their numerous and [10,11], latex technology [12], compatibilization in polymer blends [13], controlled drug delivery [14–. 17], water purification [18,19], viscosity and surface modification [20,21,22,23],[12], catalytic supports [24], polymer blends [13], controlled drug delivery [14,15,16,17], water purification [18,19], viscosity and surface lithographic templates [25], nanoreactors [26,27], etc.

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