Surface Studies of Polymer Blends by Sum Frequency Vibrational Spectroscopy, Atomic Force Microscopy, and Contact Angle Goniometry

Abstract

The surface composition, surface structure, and wetting properties of a polymer blend were studied by a combination of surface-sensitive techniques: IR + visible sum-frequency generation vibrational spectroscopy (SFG), atomic force microscopy (AFM), and contact angle goniometry. The polymer blend studied is composed of Biospan-S (BS) and a phenoxy base polymer (BP). BS is a polyurethane, capped with poly(dimethylsiloxane) (PDMS) end groups, and has a water contact angle of 94°. BP is more hydrophilic with a water contact angle of 74°. The SFG study shows that the more hydrophobic BS component likes to segregate to the blend surface in air and approaches a full surface coverage when the BS bulk concentration is only 1.7 wt %. The surface density of BS decreases with the decrease of its bulk concentration from 1.7 wt % and becomes undetectable at the surface, at a bulk concentration of 0.17 wt %. The surface free energy of the blend varies accordingly, as seen from the contact angle measurements. The AFM study also shows that the blend surface is predominantly occupied by BP for BS bulk concentrations lower than 0.17 wt % and by BS for BS bulk concentrations higher than 1.7 wt %. It reveals a domain pattern in the intermediate region when BS and BP coexist on the surface. The combined information obtained by SFG, AFM, and contact angle goniometry provides a more detailed understanding of interfacial phenomenon of blended macromolecular systems at the molecular level.

Rapidly Biodegrading PLGA-Polyurethane Fibers for Sustained Release of Physicochemically Diverse Drugs

“…On a bulk polymer level, there were no major differences in wettability, and all polymers exhibited a mixed hydrophobic and hydrophilic nature. 52 This is supported by our XPS and polymer degradation results, as enrichment of fluorine on the film or fiber surface would likely cause an observable increase in hydrophobicity and slower degradation; however, the polymers did not exhibit differences in wettability or degradation. In particular, our PLGA-based biodegradable PU all degraded more quickly than previously reported PCL-based polyurethanes 26,53,54 and showed <20% mass remaining after 4 weeks.…”

Investigating buried polymer interfaces using sum frequency generation vibrational spectroscopy

“…A review on SFG studies of polymer surfaces and interfaces was published in 2002 [7] which mainly summarized SFG research of polymer surface structures in air and water. For example, SFG has been extensively applied to study many different polymers in air, such as polyethylene (PE), polypropylene (PP) [9,10], polymethacrylates [11,12], polystyrene (PS) [13,14], polyimide [15], polyvinyl alcohol [16,17], Teflon [18], various polymer blends [19–22], copolymers [23], and polymer surfaces after modification [24–27]. Such research will not be discussed in this article.…”

Wettability of the morphologically and compositionally varied surfaces prepared from blends of well ordered comb-like polymer and polystyrene

“…Among the many methods for modifying the surface properties, polymer blending is considered one of the simplest methods for obtaining the desirable surface characteristics by controlling the surface morphology and wettability [6][7][8][9][10][11][12][13][14][15] and commercially available polystyrene (PS) and poly(methyl methacrylate) (PMMA) have been studied extensively as blending components [16][17][18][19][20][21][22][23]. Polymer surfaces with extremely low surface energies are used widely in electric and biomedical applications [24][25][26].…”