The Effect of Poly(ethylene glycol) (PEG) Length on the Wettability and Surface Chemistry of PEG-Fluoroalkyl-Modified Polystyrene Diblock Copolymers and Their Two-Layer Films with Elastomer Matrix.

Elisa Guazzelli,Giancarlo Galli,Elisa Martinelli

doi:10.3390/polym12061236

Elisa Guazzelli, Giancarlo Galli + Show 1 more

Open Access

https://doi.org/10.3390/polym12061236

Copy DOI

Journal: Polymers	Publication Date: May 29, 2020
Citations: 13	License type: CC BY 4.0

Affiliation: University of Pisa

Abstract

Diblock copolymers composed of a polystyrene first block and a PEG-fluoroalkyl chain-modified polystyrene second block were synthesized by controlled atom transfer radical polymerization (ATRP), starting from the same polystyrene macroinitiator. The wettability of the polymer film surfaces was investigated by measurements of static and dynamic contact angles. An increase in advancing water contact angle was evident for all the films after immersion in water for short times (10 and 1000 s), consistent with an unusual contraphilic switch of the PEG-fluoroalkyl side chains. Such a contraphilic response also accounted for the retained wettability of the polymer films upon prolonged contact with water, without an anticipated increase in the hydrophilic character. The copolymers were then used as surface-active modifiers of elastomer poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS)-based two-layer films. The elastomeric behavior of the films was varied by using SEBS matrices with different amounts of polystyrene. Whereas the mechanical properties strictly resembled those of the nature of the SEBS matrix, the surface properties were imposed by the additive. The contraphilic switch of the PEG-fluoroalkyl side chains resulted in an exceptionally high enrichment in fluorine of the film surface after immersion in water for seven days.

Highlights

Polymer surface-active additives are used to modify and opportunely modulate the surface properties of the polymer matrix into which they are incorporated—either physically dispersed [1,2,3,4,5,6,7,8]or chemically linked [9,10,11,12,13,14,15]
Whereas the mechanical properties strictly resembled those of the nature of the SEBS matrix, the surface properties were imposed by the additive
Diblock copolymers S27SzAn were synthesized according to a two-step procedure reported in [6]

Summary

Introduction

Polymer surface-active additives are used to modify and opportunely modulate the surface properties of the polymer matrix into which they are incorporated—either physically dispersed [1,2,3,4,5,6,7,8]or chemically linked [9,10,11,12,13,14,15]. By taking advantage of the ability of the additive to selectively segregate at the surface of a polymer film, the wettability properties are commonly changed [16,17,18,19]. Several factors are known to affect the surface segregation of the polymer additive, including its molar mass, chemical structure, composition, surface tension and chemical compatibility with the host matrix [20,21,22,23,24]. Polyethylene glycol-based surface-active additives are exploited to promote a non-ionic hydrophilic behavior in a polymer film surface, and improve its antifouling properties against proteins, bacteria, cells and marine organisms [31,32,33]

Methods

Results

Conclusion