01911nas a2200169 4500008004100000022001400041245005100055210005100106260007100157300001400228490000700242520133200249100002801581700002201609700002701631856008301658 2016 eng d a0897-475600aOmniphilic polymeric sponges by ice templating0 aOmniphilic polymeric sponges by ice templating a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcMAR a1823-18310 v283 a

Sponges that absorb a large quantity of solvent relative to their weight, independent of the solvent polarity, represent useful universal absorbents for laboratory and industrial spills. We report the preparation of macroporous polymer sponges by ice templating of polyethylenimine aqueous solutions and their cross-linking in the frozen state. The as-prepared monolith is hydrophilic and absorbs over 30 fold its weight in water. Modification of this sponge using valeroyl chloride renders it omniphilic; viz., a modified sponge absorbs over 10-fold its dry weight of either water or hexane. Modification using palmitoyl chloride that has a longer chain length results in the preparation of a hydrophobic sponge with a water contact angle around 130, which retains its oleophilicity underwater. The solvent absorbed in these sponges can be simply squeezed out, and the sponges are stable to several hundred cycles of compression. The large pore sizes of these sponges allow rapid absorption of even high viscosity solvents such as pump oil. Finally, we demonstrate that these sponges are also able to separate apolar oils that are emulsified in water using surfactants. These high porosity sponges with controllable solvophilicity represent inexpensive, high performance universal absorbents for general solvent spills.

1 aChatterjee, Soumyajyoti1 aGupta, Sayam, Sen1 aKumaraswamy, Guruswamy uhttps://library.ncl.res.in/content/omniphilic-polymeric-sponges-ice-templating02767nas a2200265 4500008004100000022001400041245005700055210005700112260000800169490000700177520201300184653001302197653002002210653002202230653001902252653001302271653000902284653002002293653001702313653000902330100002802339700001802367700002702385856008902412 2017 eng d a1744-683X00aCapillary uptake in macroporous compressible sponges0 aCapillary uptake in macroporous compressible sponges cSEP0 v133 a

The capillarity-driven uptake of liquid in swellable, highly porous sponges is of significant industrial importance. Sponges prepared using polymers and their composites with carbon nanotubes and graphene have been reported, with extraordinary solvent uptake capacities and with the ability to separate oil from water. However, the effect of systematic variation of sponge characteristics on solvent uptake has not been investigated. Here, we report experiments that study capillary uptake in a variety of flexible, centimetre-sized macroporous cylindrical sponges. We used ice-templating to prepare a series of model macroporous sponges in which the porosity, modulus and composition were systematically varied. We investigated two kinds of sponge: (a) those composed purely of cross-linked polymers and (b) those prepared as composites of inorganic particles and polymers. Both kinds of sponge are flexible and exhibit elastic recovery after large compressive deformation. All sponges were characterized thoroughly with respect to their pore microstructure and elastic modulus. When one end of a sponge is plunged into a large reservoir, water rises through capillary action against gravity. We observed a transition from an inertial capillary regime, where the liquid column height rose linearly with time, t, to a viscous capillary regime, where the liquid height rose with time t(0.5). We showed that these results can be rationalized using analyses developed for rigid sponges. We combined differential momentum balance equations for uptake in rigid capillaries with the phenomenological Ergun-Forchheimer relations to account for the effect of the sponge microstructure. This approach works remarkably well in the viscous capillary regime and shows that capillary uptake is governed primarily by the total porosity and pore dimensions of soft sponges.

10aaerogels10aBuilding blocks10aCatalyst Supports10aContact-angels10aDynamics10aflow10aOrganic Liquids10aPorous-Media10aRise1 aChatterjee, Soumyajyoti1 aDoshi, Pankaj1 aKumaraswamy, Guruswamy uhttps://library.ncl.res.in/content/capillary-uptake-macroporous-compressible-sponges02476nas a2200169 4500008004100000245010500041210006900146260000800215300001400223490000800237520182600245100001902071700002802090700002702118700003102145856013002176 2017 eng d00aElastic compressible energy storage devices from ice templated polymer gels treated with polyphenols0 aElastic compressible energy storage devices from ice templated p cFEB a3270-32780 v1213 aDesign and fabrication of rechargeable energy storage devices that are robust to mechanical deformation is essential for wearable electronics. We report the preparation of compressible supercapacitors that retain their specific capacitance after large compression and that recover elastically after at least a hundred compression expansion cycles. Compressible supercapacitors are prepared using a facile, scalable method that readily yields centimeter-scale macroporous objects. We ice template a solution of polyethylenimine in green tea extract to prepare a macroporous cross-linked polymer gel (PG) whose walls are impregnated with green tea derived polyphenols. As the PG is insulating, we impart conductivity by deposition of gold on it. Gold deposition is done in two steps: first, silver nanoparticles are formed on the PG walls by in situ reduction by polyphenols and then gold films are deposited on these walls. Gold coated PGs (GPGs) were used as electrodes to deposit poly(3,4-ethylenedioxythiophene) as a pseudocapacitive material. The specific capacitance of PEDOT coated GPGs (PGPG) was found to be 253 F/g at 1 A/g. PGPG could be compressed and expanded over a hundred cycles without any suffering mechanical failure or loss of capacitative performance. The capacitance was found to be 243 F/g upon compressing the device to 25% of its original size (viz. compressive strain = 75%). Thus, even large compression does not affect the device performance. This device shows power and energy densities of 2715 W/kg and 22 Wh/kg, respectively, in the uncompressed state. The macroporous nature of PGPG makes it possible to fill the PGPG pores with gel electrolyte. We report that the gel electrolyte filled supercapacitor exhibited a specific capacitance of 200 F/g, which increased by 4% upon 75% compression.1 aDas, Chayanika1 aChatterjee, Soumyajyoti1 aKumaraswamy, Guruswamy1 aKrishnarnoorthy, Kothandam uhttps://library.ncl.res.in/content/elastic-compressible-energy-storage-devices-ice-templated-polymer-gels-treated-polyphenols02213nas a2200157 4500008004100000245008000041210006900121260000800190300001600198490000600214520163600220100002801856700003101884700002701915856011301942 2017 eng d00aFire-retardant, self-extinguishing inorganic/polymer composite memory foams0 aFireretardant selfextinguishing inorganicpolymer composite memor cDEC a44864-448720 v93 aPolymeric foams used in furniture and automotive and aircraft seating applications rely on the incorporation of environmentally hazardous fire-retardant additives to meet fire safety norms. This has occasioned significant interest in novel approaches to the elimination of fire-retardant additives. Foams based on polymer nano composites or based on fire-retardant coatings show compromised mechanical performance and require additional processing steps. Here, we demonstrate a one-step preparation of a fire-retardant ice-templated inorganic/polymer hybrid that does not incorporate fire-retardant additives. The hybrid foams exhibit excellent mechanical properties. They are elastic to large compressional strain, despite the high inorganic content. They also exhibit tunable mechanical recovery, including viscoelastic "memory". These hybrid foams are prepared using ice-templating that relies on a green solvent, water, porogen. Because these foams are predominantly comprised of inorganic components, they exhibit exceptional fire retardance in torch burn tests and are self-extinguishing. After being subjected to a flame, the foam retains its porous structure and does not drip or collapse. In micro-combustion calorimetry, the hybrid foams show a peak heat release rate that is only 25% that of a commercial fire-retardant polyurethanes. Finally, we demonstrate that we can use ice-templating to prepare hybrid foams with different inorganic colloids, including cheap commercial materials. We also demonstrate that ice-templating is amenable to scale up, without loss of mechanical performance or fire-retardant properties.1 aChatterjee, Soumyajyoti1 aShanmuganathan, Kadhiravan1 aKumaraswamy, Guruswamy uhttps://library.ncl.res.in/content/fire-retardant-self-extinguishing-inorganicpolymer-composite-memory-foams02071nas a2200217 4500008004100000022001400041245013800055210006900193260000800262300001400270490000700284520129100291100001701582700002201599700001901621700001801640700002801658700002001686700002001706856012701726 2018 eng d a0897-475600aMultistimuli-responsive interconvertible low-molecular weight metallohydrogels and the in situ entrapment of CdS quantum dots therein0 aMultistimuliresponsive interconvertible lowmolecular weight meta cJUL a4755-47610 v303 a

Two low molecular weight metallohydrogels (ZALA and CALA) have been synthesized from an amino-acid based ligand precursor (LA) and two different metal salts [zinc acetate dihydrate (ZA) and cadmium acetate dihydrate (CA), respectively. These two hydrogels show a unique chemically stimulated interconversion to each other via a reversible gel-sol gel pathway. This programmable gel-sol reversible system satisfies logic operations of a basic Boolean logic (INHIBIT) gate. Also, these hydrogels can be degraded into different MOF phases at room temperature spontaneously or in the presence of chloride and bromide salts (NaCl and NaBr.). CdS quantum dots can be grown inside the CALA gel matrix (CdS@CALA) in the presence of small amount of Na2S. This CdS doped gel exhibits time dependent tunable emission (white to yellow to orange) as a consequence of a slow agglomeration process of the entrapped quantum dots inside the gel matrix. This luminescence property also reflects the corresponding gel derived MOFs (obtained either by self-degradation of CdS@CALA or via anion induction) as well. This, to the best of our knowledge, is probably the simplest way to make a CdS quantum dot based composite material where CdS is entrapped within the gel and the gel-derived MOF matrix.

1 aBera, Saibal1 aChakraborty, Amit1 aKarak, Suvendu1 aHalder, Arjun1 aChatterjee, Soumyajyoti1 aSaha, Subhadeep1 aBanerjee, Rahul uhttps://library.ncl.res.in/content/multistimuli-responsive-interconvertible-low-molecular-weight-metallohydrogels-and-situ02105nas a2200181 4500008004100000022001400041245010500055210006900160260000800229300001600237490000600253520144600259100002801705700001801733700001601751700002701767856012901794 2018 eng d a2046-206900aPreparation of macroporous scaffolds with holes in pore walls and pressure driven flows through them0 aPreparation of macroporous scaffolds with holes in pore walls an cJAN a24731-247390 v83 a

Controlling the pore architecture in macroporous scaffolds has important implications for their use as reactor packings and as catalyst supports. We report the preparation of a macroporous structure, where the pore walls are perforated by holes. These materials are prepared by modification of the ice-templating protocol developed in our group. We freeze a dispersion of colloidal silica, polymer and cross-linker in a water/acetonitrile medium and allow crosslinking to proceed in the frozen state. The presence of a small fraction of acetonitrile (varying between 1.6% to 6.4%) results in the formation of holes in the pore walls. Increasing the acetonitrile concentration changes the pore size distribution, and produces smaller pores on average. This also results in an increasing fraction of the wall area being covered by small pores, of the order of a few microns in size. Perforation of the walls by pores does not change the overall porosity or modulus of the scaffolds. However, the introduction of pores leads to a drastic reduction in the pressure drop required to pump liquid through the scaffolds. The observed residence time distribution (RTD) in the scaffolds is represented by two plug flow reactors (PFRs) in parallel. The RTD results indicate that increasing the hole fraction in the pore walls results in increased channelling which explains the aforementioned decreased pressure drop during pressure driven flow.

1 aChatterjee, Soumyajyoti1 aPotdar, Aditi1 aKuhn, Simon1 aKumaraswamy, Guruswamy uhttps://library.ncl.res.in/content/preparation-macroporous-scaffolds-holes-pore-walls-and-pressure-driven-flows-through-them