Effect of surfactant type on surfactant-maltodextrin interactions: isothermal titration calorimetry, surface tensiometry, and ultrasonic velocimetry study

Isothermal titration calorimetry (ITC), surface tensiometry, and ultrasonic velocimetry were used to characterize surfactant-maltodextrin interactions in buffer solutions (pH 7.0, 10 mM NaCl, 20 mM Trizma base, 30.0 degrees C). Experiments were carried out using three surfactants with similar nonpolar tail groups (C12) but different charged headgroups: anionic (sodium dodecyl sulfate, SDS), cationic (dodecyl trimethylammonium bromide, DTAB), and nonionic (polyoxyethylene 23 lauryl ether, Brij35). All three surfactants bound to maltodextrin, with the binding characteristics depending on whether the surfactant headgroup was ionic or nonionic. The amounts of surfactant bound to 0.5% w/v maltodextrin (DE 5) at saturation were < 0.3 mM Brij35, approximately 1-1.6 mM SDS, and approximately 1.5 mM DTAB. ITC measurements indicated that surfactant binding to maltodextrin was exothermic. Surface tension measurements indicated that the DTAB-maltodextrin complex was more surface active than DTAB alone but that SDS- and Brij35- maltodextrin complexes were less surface active than the surfactants alone.     

Facile synthesis of nanoparticles via assembly of photopolymerized and self‐crosslinked random copolymers in selective organic media

We report the facile synthesis of vesicular nanoparticles via self‐assembly of random copolymers in selective organic solvents. The polymers were synthesized via photopolymerization in bulk from acryloyl chloride (AC) containing a small amount of hydrolyzed acrylic acid (AA) at ambient condition. Fourier transform infrared spectroscopy of the photopolymerized product revealed two main chemical components: poly(acryloyl chloride) (PAC) and acid anhydride. The later peak intensified when increasing the initial AA composition in the monomer solution, suggesting that the hydrolyzed AC contributed to the formation of crosslinked anhydride, leading to amphiphilicity of the polymer with solvophobic anhydride and solvophilic PAC chains. At an optimal UV dosage (2000 mJ cm^?2), vesicular nanoparticles (～90 nm in diameter) were obtained from polymers assembled in acetone. The particle size and morphology were confirmed by scanning electron microscopy, transmission electron microscopy, and dynamic and static light‐scattering measurements. Further, we found that the random copolymers self‐organized into vesicles in merely good solvents of PAC chains, including acetonitrile, tetrahydrofuran, and 1,4‐dioxane, but became aggregated and precipitated out in poor solvents of PAC, such as isopropanol, ethanol, toluene, xylene, and hexane. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis of dual‐functional copolymer with orthogonally photosensitive groups

A dual‐functional copolymer, poly(4‐styrenesulfonyl azide‐co‐t‐butyl‐methacrylate), with built‐in photoacid labile and photocrosslinkable components was designed and synthesized by radical copolymerization. The mixture of copolymer and photoacid generators was spin coated on aminosilane treated Si wafers and polycarbonate (PC). When exposed to 365 nm UV light, photoacids were generated, which decomposed the acid labile groups, t‐butyl‐ester, to carboxylic acid in the exposed region, leading to drastic change of wettability from hydrophobic to hydrophilic after developing the film in an aqueous base solution. The patterned polymer film could be subsequently photoimmobilized on the substrate under 254 nm deep UV exposure through C? H insertion via exited azide groups. ¹H‐NMR and Fourier transform infrared spectra confirmed the synthesis of the copolymer, and the photodecomposition and photografting reactions occurred orthogonally at 365 and 254 nm, respectively, without interfering each other. On the patterned surfaces, including a hexagonal dot array and a gradient line array, we demonstrated selective wetting in the 365 nm exposed regions. On the gradient line array, we showed an interesting ratchet wetting pattern. Finally, we showed that the copolymer could be used to modify the wettability of PC while maintaining its high optical quality. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013