The use of a fatty acid/?-Hydroxyester blend to enhance the surface hydrophilicity of crosslinked poly(ethylene glycol) coatings

Article

Authorship

Ruiz, Mariano Manuel ; SCHROEDER, WALTER FABIAN ; HOPPE, CRISTINA ELENA

Date

2019

Publishing House and Editing Place

ELSEVIER SCIENCE SA

Magazine

PROGRESS IN ORGANIC COATINGS, vol. 135 (pp. 313-320) ELSEVIER SCIENCE SA

Summary Information provided by the agent in SIGEVA

By reaction between stearic acid (SA) and a di-epoxidized oligomeric poly(ethylene glycol) under stoichiometric conditions, an amphiphilic ?-hydroxyester (?-HE) bearing pendant alkyl chains was obtained with a typical yield of 93 wt%. The remaining 7 wt% consisted of SA. This blend, named ?-HESA, was used as modifier of a reactive solvent based on poly(ethyleneglycol) dimethacrylate (PEGDMA). The system was activated with a visible-light photoinitiator, and crosslinked films were obtained after... By reaction between stearic acid (SA) and a di-epoxidized oligomeric poly(ethylene glycol) under stoichiometric conditions, an amphiphilic ?-hydroxyester (?-HE) bearing pendant alkyl chains was obtained with a typical yield of 93 wt%. The remaining 7 wt% consisted of SA. This blend, named ?-HESA, was used as modifier of a reactive solvent based on poly(ethyleneglycol) dimethacrylate (PEGDMA). The system was activated with a visible-light photoinitiator, and crosslinked films were obtained after five minutes of irradiation. A drastic change in the contact angle from 43.2° to 14.6° was attained by adding only 10 wt% of ?-HESA, indicating that this modifier had a profound effect on the surface hydrophilicity of the films. Morphological analysis showed that a phase separation process took place in these modified systems that led to the formation of ?-HESA-rich crystalline domains dispersed in an amorphous phase mostly formed by cross-linked PEGDMA. An explanation for the marked increase of the surface hydrophilicity of the films was found both in the formation of a micro-structured surface texture and in the orientation of polar groups of SA towards the solid-air interface. This interpretation was based on the evidence that crystals were formed by fully extended n-alkyl chains of the ?-HE which were interdigitated by chains of free SA. This configuration allowed accommodating free SA chains within the same crystal structure of the ?-hydroxyester and exposing the polar carboxylic acid groups of SA towards the air/polymer interface. The results of this work show that the combination of a phase separation process with the proper design and arrangement of amphiphilic molecules can lead to a unique surface behavior with potential interest in technological applications.