Thermotropic polymers with the capability of thermally tuning transparency are widely applied in smart windows and energy-saving windows, playing a critical role in enhancing comfort level and energy efficiency of indoor spaces. Usually, thermotropic polymer systems are constructed by physically dispersing phase transition materials in transparent hosting materials. However, bad interfaces universally exist in these systems, resulting in poor mechanical properties, weak interfaces to substrates, or bad long-term stability. Herein, we demonstrate a novel chemically interconnected thermotropic polymer, which is obtained by reacting dodecanedioic acid (DDA) with glycerol. In the system, some of DDA molecules were cross-linked to form a polyester network, poly­(glycerol-dodecanoate) (PGD). Other grafted but non-cross-linked DDA molecules form semicrystalline domains, which possess a solid–liquid phase transition within the PGD matrix. The phase transition offers the resulting hybrid materials with tunable optical transparency. The PGD–DDA system shows stable performance after 100 heating–cooling cycles. In addition, when applied for window coating, it results in tough interfacial bonding to glass substrates with toughness of >6910 J m–2 below its transition temperature and >135 J m–2 above its transition temperature. It increases the impact resistance of the window by multiple times.

In recent studies, polyurethane has shown multiple properties that make it an excellent candidate material in 4D printing. In this study, we present a simple and inexpensive additive method to print waterborne polyurethane paint-based composites by adding carboxymethyl cellulose (CMC) and silicon oxide (SiO 2) nanoparticles to the paint. The first function of CMC and SiO 2 is to improve rheological properties of the polyurethane paint for making a printable precursor, which improves the printing resolution and enhances additive manufacturability. Second, the composite precursors improve the curing rate of the polyurethane paint without changing its inherited shape memory properties. Third, the printed composite parts shown enhanced mechanical strength compared with that of the parts printed with pure polyurethane. Finally, the 3D printed polyurethane-CMC and SiO 2 parts exhibit time-resolved shape transformation upon heat stimulation. To the best of our knowledge, this is the first study of using the polyurethane paint as the precursor for 4D printing, which would open new possibilities in future applications in biomedical engineering, soft robotics and so on.

We report the results of analyses of detrital zircon from the middle Cambrian Flathead Sandstone from four locations in Park County, WY. The Flathead U-Pb zircon age spectra (n=355) includes one peak at 2702–3345 Ma (95%) and two small age peaks at 1784 Ma (4%) and ∼1830 Ma (1%). Regional paleocurrent data for the Flat-head indicate sediment transport from east to west but the dominant Archean detrital zircons in our sample suite indicates a proximal source in structurally and topographically high Wyoming Province crust. The Archean ages are consistent with the >3.0 Ga fraction being derived from basement rocks present in the northern Beartooth Range and areas further to the west. The 2.8–3.0 Ga grains were derived from the Beartooth-Bighorn magmatic zone, which directly underlies and extends to the south and east of these Flathead sampling localities. The 1.7–1.8 Ga grains were derived from 100s of km to the south and east, in the Cheyenne Belt or more distal Yavapai Province rocks. This 1.7–1.8 Ga crust was uplifted along the Transcontinental Arch during late Precambrian time. The Transcontinental Arch, and perhaps the Midcontinent Rift further to the east as well, prevented easterly-sourced (i.e. Grenville) zircons from reaching the Wyoming Sauk shoreline.

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