Applications of Fast, Facile, Radiation-Free Radical Polymerization Techniques Enabled by Room Temperature Alkylborane Chemistry.

Fast, robust, and scalable techniques for covalent materials assembly are shown to be enabled by variants of a simple mixing-induced free radical initiation scheme broadly termed room-temperature alkylborane (RTA) chemistry. Unique process versatility, speed of reaction, high conversion, and structural control at ambient conditions occur by exploiting air-stable alkylborane-amine complexes that rapidly initiate upon mixing with common amine-reactive decomplexing agents such as carboxylic acid compounds. Three diverse application examples are presented, illustrating facile ambient routes to covalent assembly varying in length scale: (1) copolymers with controllable pressure-sensitive adhesive properties, (2) hydrophilically modified silicone microparticles from heterophase reactions, and (3) UV-free inkjet printable materials suitable for thick-textured patterning and printing, all conducted in open air with no radiation or atmospheric control.

Amide bond cleavage: acceleration due to a 1,3-diaxial interaction with a carboxylic acid.

To independently assess the contribution of ground-state pseudoallylic strain to the enormous rates of amide bond cleavage in tertiary amide derivatives of Kemp's triacid, we have studied four amide derivatives of (1alpha-3alpha-5beta)-5-tert-butyl-1,3-cyclohexanedicarboxylic acid. Our results demonstrate that absent pseudoallylic strain, a 1,3-diaxial interaction of an amide with a carboxylic acid leads to only a 2400-fold increase in the rate of amide bond cleavage as compared with the rate of hydrolysis of an unactivated peptide bond.

Two-dimensional fluidics based on differential lyophobicity and gravity.

We have prepared planar fluidics devices using binary chemical patterns consisting of hydrophobic "roads" on which water droplets slide easily and more hydrophobic "curbs" that direct droplet motion. Contact angle and contact angle hysteresis both control the motion of liquid droplets on surfaces. The difference between the advancing contact angles of the two regions prevents the liquid from crossing the interface between them.

Condensation on ultrahydrophobic surfaces and its effect on droplet mobility: ultrahydrophobic surfaces are not always water repellant.

The condensation of water was studied on topography-based ultrahydrophobic surfaces containing hydrophobized silicon pillars. Optical microscopy showed that water nucleated and grew both on top of and between the pillars. As condensation progressed, water between the pillars became unstable and was forced upward to the surface.