A Low-Voltage, High-Force Capacity Electroadhesive Clutch Based on Ionoelastomer Heterojunctions

Electroadhesive devices with dielectric films can electrically program changes in stiffness and adhesion, but require hundreds of volts and are subject to failure by dielectric breakdown. Recent work on ionoelastomer heterojunctions has enabled reversible electroadhesion with low voltages, but these materials exhibit limited force capacities and high detachment forces. It is a grand challenge to engineer electroadhesives with large force capacities and programmable detachment at low voltages (<10 V). In this work, tough ionoelastomer/metal mesh composites with low surface energies are synthesized and surface roughness is controlled to realize sub-ten-volt clutches that are small, strong, and easily detachable. Models based on fracture and contact mechanics explain how clutch compliance and surface texture affect force capacity and contact area, which is validated over different geometries and voltages. These ionoelastomer clutches outperform the best existing electroadhesive clutches by fivefold in force capacity per unit area (102 N cm-2 ), with a 40-fold reduction in operating voltage (± 7.5 V). Finally, the ability of the ionoelastomer clutches to resist bending moments in a finger wearable and as a reversible adhesive in an adjustable phone mount is demonstrated.

Fluorescence imaging of nanoscale domains in polymer blends using stochastic optical reconstruction microscopy (STORM)

High-resolution fluorescence techniques that provide spatial resolution below the diffraction limit are attractive new methods for structural characterization of nanostructured materials. For the first time, we apply the super-resolution technique of Stochastic Optical Reconstruction Microscopy (STORM), to characterize nanoscale structures within polymer blend films. The STORM technique involves temporally separating the fluorescence signals from individual labeled polymers, allowing their positions to be localized with high accuracy, yielding a high-resolution composite image of the material. Here, we describe the application of the technique to demixed blend films of polystyrene (PS) and poly(methyl methacrylate) (PMMA), and find that STORM provides comparable structural characteristics as those determined by Atomic Force Microscopy (AFM) and scanning electron microscopy (SEM), but with all of the advantages of a far-field optical technique.

Chemistry of the Podocarpaceae. LXIV. Studies in the ambergris odorant field

The cyclic ethers 17-nor-16-oxa-l3β-kaurane (8) and 15,16-epoxy-17-nor-15,16-seco-8β,13β-kaurane (11) have been prepared from 13 β-kaur-15-ene ('isophyllocladene')(1) and 13 β-kaur-16-ene ('phyllocladene') (2), respectively. The derivative (8), but not (11), possesses an ambergris-type odour. Preparation of the 8 β,12-epoxides (30),(31),(33) and (34) from 12-hydroxypodocarpa-8,11,13-trien-19-oic acid ('podocarpic acid') (3) indicates that substitution of the 4β-methyl group destroys their potentially odoriferous nature. An attempt to prepare epimers of the C8 demethyl analogue of the known ambergris-type odorant (45) is reported; a mixture of the C13 epimers of (45) is readily prepared from the unsaturated ketone (41).

Chemistry of the Podocarpaceae. LXIII. Ring-C oxidation of totarol

Methods for the conversion of totarol (1) into the catechol derivative (2) are described. Oxidative cleavage of the derived methyl ether (13) by ozonolysis affords a high-yielding route to a compound (34) with potential as a nagilactone precursor.

A reinvestigation of the Prévost reaction with N-allylmorpholine

A reinvestigation of the Prevost reaction of N-allylmorpholine (1) with silver(I) benzoate and iodine shows that it gives the 1,3-dibenzoate (2) (11%) through rearrangement, the 1,2-dibenzoate (3) (5%) and (1) (13%).

The Crystal Structure of 8β-Hydroxymethylpodocarpane-13β-carboxylic Acid Lactone: the Circular Dichroism of This and Some Related Lactones

The title compound crystallizes in the orthorhombic space group P212121 with cell dimensions of a 7.313(1), b 9.093(1), c 24.514(2) �. The structure was solved by direct methods from diffractometer data and refined by the method of least squares to an R of 0.050; bond lengths and angles are normal although the bridged lactone ring exhibits an unexpected conformation. Circular dichroism spectra have been obtained from the title compound and five related lactones, all of which are similar in that the lactone group extended by an extra carbon atom (C-CO-O or CO-O-C) forms a 1,3 bridge across a six-membered ring. For two of the compounds, the c.d. within the region of the n → p* transition is bisignate. We conclude that the correlations between structure and n → p* c.d. sign previously adduced for bridged-ring lactones do not extend to lactones of this type.

Chemistry of the Podocarpaceae. LII. Demethylation involving partial inversion of cofiguration at two remote centres

Treatment of optically pure (+)-12-methoxypodocarpa-8,11,13-triene (2) with HI/HBr/HOAc and a trace of H3PO2 gives, as the major product, a non-racemic mixture of (+)-podocarpa-8,11,13-trien-12-ol (3) and its enantiomer (14).

Chemistry of the Podocarpaceae. LI. Ozonolysis products of Podocarpa-8,11,13-trien-12-ol

Podocarpa-8,11,13-trien-12-ol (2) has been converted by ozonolysis and subsequent transformations into the lactone (13), a tobacco flavouring agent, and into the bicyclic acetate (11) , a compound with a woody odour.

Chemistry of the Podocarpaceae. XLVII. Steroidal analogues from 12-Hydroxypodocarpa-8,11,13-trien-19-oic acid

Attempts to utilize the ketones (10) and (11) for the preparation of steroidal analogues are described. The ketone (10) has been converted into the octahydrochrysene (26) and to the benzindene derivative (29). The diketone (16) has been converted into the de-A pregnane derivative (27) and by auto-cyclization to the ketol (8) and the ketone (34).

Chemistry of the Podocarpaceae. XLIX. Isomerization of 12-Methoxy-19-norpodocarpatetraenes

Methods for isomerization of the 12-methoxy-19-norpodocarpatetraene mixture obtained from oxidative decarboxylation of 12-methoxypodocarpa-8,11,13-trien-19-oic acid (1) with lead tetraacetate have been examined. Acid-catalysed isomerization gives a mixture of the endocyclic isomers (11) and (19) while iodine-catalysed isomerization gives a mixture enriched in the isomer (19) to the extent of 80%. Metal-catalysed decarbonylation of the acid chloride (6) and oxidative decarboxylation of the acetoxy acid (7) have also been examined.

Chemistry of the Podocarpaceae. XLVIII. Photo-sensitized oxidations of unsaturated ring-c aromatic diterpenoids

Photo-sensitized oxidation of the 6,7-dehydro ring-c aromatic diterpenoids (5), (8) and (38) affords high yields of the corresponding 5-ene-7-ones (62), (63) and (69). Similar oxygenation of 13-methoxy- totara-6,8,11,13-triene (21) gives a hydroperoxide (74) which undergoes a facile rearrangement to a naphthyl derivative (80) in the presence of acid. Photo-sensitized oxidation of the enol acetates derived from the 7-oxo diterpenoids, however, provides a general method for preparation of the corresponding 5-ene-7-one. Reduction of the enone (62) with lithium aluminium hydridealuminium chloride gives a mixture of the 5,8,11,13-tetraene (66) and the 6,8,11,13-tetraene (9) while reduction with sodium borohydride and treatment of the resulting alcohols (61) and (67) with acid gives a mixture of the tetraenes (5) and (68). Photo-oxygenation of the latter mixture provides a convenient method for isolating the tetraene (68). Similar reductions of 13-methoxytotara-5,8,11,13-tetraen-7-one (76) have been examined and products from the action of m-chloroperbenzoic acid on the enol acetates (19), (20) and (7) are reported.

Chemistry of the Podocarpaceae. L. Conversion of 12-Hydroxypodocarpa-8,11,13-trien-19-oic acid (podocarpic acid) into 19-Hydroxypodocarp-8(14)-en-13-one

Detosylations of derivatives of methyl 12-toluene-p- sulphonyloxypodocarpa-8,11,13-trien-19-oate have been investigated using a modified W-7 Raney nickel catalyst. The final steps in a conversion of podocarpic acid (1) into (+)-19-hydroxypodocarp-8(14)-en- 13-one (21), a useful intermediate for synthesis, have been effected.

Chemistry of the Podocarpaceae. XXXVII. Oxidative degradations of phyllocladene and isophyllocladene : conversion of isophyllocladene into (+)-Podocarp-8(14)-en-13-one

The ozonolysis of phyllocladene (2) and isophyllocladene (12) has been carried out under a number of different conditions and the ozonide (34) of isophyllocladene has been isolated and characterized. Conversion of phyllocladene (2) into the diacid (20) has been accomplished by several routes from the norketone (3). Isophyllocladene (12) has been converted into (+)-podocarp-8(14)-en-13-one (1), an optically active relay which is useful in synthesis. The route involves ozonolysis of isophyllocladene, Baeyer-Villiger oxidation of the keto aldehyde (25), lithium aluminium hydride reduction of the ester (27), and chromium trioxide-pyridine oxidation of the resulting keto aldehyde (32) which gives the keto acid (30) in 26% overall yield. Oxidative decarboxylation then affords the enone (1) in 14% yield.