Hexagonally ordered arrays of metallic nanodots from thin films of functional block copolymers

We demonstrate a new and simple route to fabricate highly dense arrays of hexagonally close packed inorganic nanodots using functional diblock copolymer (PS-b-P4VP) thin films. The deposition of pre-synthesized inorganic nanoparticles selectively into the P4VP domains of PS-b-P4VP thin films, followed by removal of the polymer, led to highly ordered metallic patterns identical to the order of the starting thin film. Examples of Au, Pt and Pd nanodot arrays are presented. The affinity of the different metal nanoparticles towards P4VP chains is also understood by extending this approach to PS-b-P4VP micellar thin films. The procedure used here is simple, eco-friendly, and compatible with the existing silicon-based technology. Also the method could be applied to various other block copolymer morphologies for generating 1-dimensional (1D) and 2-dimensional (2D) structures. (c) 2010 Elsevier Ltd. All rights reserved.

A low-cost lead-acid battery with high specific-energy

Lightweight grids for lead-acid battery grids have been prepared from acrylonitrile. butadiene styrene (ABS) copolymer followed by coating with lead. Subsequently, the grids have been electrochemically coated with a conductive and corrosion-resistant layer of polyaniline. These grids are about 75% lighter than those employed in conventional lead-acid batteries. Commercial-grade 6V/3.5 Ah (C-20-rate) lead-acid batteries have been assembled and characterized employing positive and negative plates constituting these grids. The specific energy of such a lead-acid battery is about 50 Wh/kg. The batteries can withstand fast charge-discharge duty cycles.

Studies on a nanocomposite solid polymer electrolyte with hydrotalcite as a filler

We have prepared a new nanocomposite polymer electrolyte using nanoparticles of hydrotalcite, an anionic clay, as the filler. Hydrotalcite has the chemical composition [M-1-x(2+) M-x(3+) (OH)(2)](x+) [A(x/n)(n-)center dot mH(2)O] where M2+ is a divalent cation (e.g. Mg2+, Ni2+, Co2+,etc.) and M3+ is a trivalent cation (e.g. Al3+, Fe3+, Cr3+, etc.). A(n-) is an anion intercalated between the positively charged double hydroxide layers. The nanoparticles of [Mg0.67Al0.33 (OH)(2)] [(CO3)(0.17)center dot mH(2)O] were prepared by the co-precipitation method (average particle size as observed by TEM similar to 50 nm) and were doped into poly(ethylene glycol) PEG (m.w.2000) complexed with LiCIO4. Samples with different wt.% of hydrotalcite were prepared and characterized using XRD, DSC, TGA, impedance spectroscopy and NMR. Ionic conductivity for the pristine sample, similar to 7.3 x 10(-7) S cm(-1), was enhanced to a maximum of = 1.1 x 10(-5) S cm(-1) for 3.6 wt.% nanoparticle doped sample. We propose that the enhancement of ionic conductivity is caused by percolation effects of the high conductivity paths provided by interfaces between the nanoparticles and the polymer electrolyte. (C) 2010 Elsevier B.V. All rights reserved.

Photoluminescence spectroscopy and lifetime measurements from self-assembled semiconductor-metal nanoparticle hybrid arrays

We present results of photoluminescence spectroscopy and lifetime measurements on thin film hybrid arrays of semiconductor quantum dots and metal nanoparticles embedded in a block copolymer template. The intensity of emission as well as the measured lifetime would be controlled by varying the volume fraction and location of gold nanoparticles in the matrix. We demonstrate the ability to both enhance and quench the luminescence in the hybrids as compared to the quantum dot array films while simultaneously engineering large reduction in luminescence lifetime with incorporation of gold nanoparticles. (C) 2010 American Institute of Physics. [doi:10.1063/1.3483162].

Controlled photoluminescence from self-assembled semiconductor-metal quantum dot hybrid array films

Thin films of hybrid arrays of cadmium selenide quantum dots and polymer grafted gold nanoparticles have been prepared using a BCP template. Controlling the dispersion and location of the respective nanoparticles allows us to tune the exciton-plasmon interaction in such hybrid arrays and hence control their optical properties. The observed photoluminescence of the hybrid array films is interpreted in terms of the dispersion and location of the gold nanoparticles and quantum dots in the block copolymer matrix.

Miscibility of poly(phenyl acrylate) with acrylonitrile/styrene copolymers

The Blase transition and phase behavior of blends of poly(pheny1 acrylate) with poly(acrylonitri1eco-styrene) was studied by differential scanning calorimetry. It was found that poly(pheny1 acrylate) is miscible with poly(acrylonitri1e-co-styrenes) within a specific range of copolymer composition. The segmental interaction parameters were estimated and found to be positive for all three pairs. The miscibility in thissystem appears to be the consequence of the intramolecular repulsion between styrene and acrylonitrile units.

Kohdennetut nanopartikkelit ja isotooppikuvantaminen syövän hoidossa

Syövän diagnostiikassa ja hoidossa nanopartikkelit voivat toimia kuljetinaineina lääke- ja diagnostisille aineille tai nukleiinihappojaksoille. Kantaja-aineeseen voidaan liittää kohdennusmolekyylejä partikkelien passiivista tai aktiivista kohdennusta varten tai radioleima kuvantamista tai radioterapiaa varten. Kantaja-aineiden avulla voidaan parantaa lääkeaineen fysikaalis-kemiallisia ominaisuuksia ja biologista hyötyosuutta, vähentää systeemisiä sivuvaikutuksia, pidentää lääkeaineen puoliintumisaikaa ja siten harventaa annosteluväliä, sekä parantaa lääkeaineen pääsyä kohdekudokseen. Näin voidaan parantaa kemo- ja radioterapian tehoa ja hoidon onnistumisen todennäköisyyttä. Kirjallisuuskatsauksessa perehdytään nanokantajien rooliin syövän hoidossa. Vuosikymmeniä jatkuneesta tutkimuksesta huolimatta vain kaksi (Eurooppa) tai kolme (Yhdysvallat) nanopartikkeliformulaatiota on hyväksytty markkinoille syövän hoidossa. Ongelmina ovat riittämätön hakeutuminen kohdekudokseen, immunogeenisyys ja nanopartikkelien labiilius. Kokeellisessa osassa tutkitaan in vitro ja hiirillä in vivo 99mTc-leimattujen, PEG-verhoiltujen biotiiniliposomien kaksivaiheista kohdennusta ihmisen munasarjan adenokarsinoomasoluihin. Kohdentamiseen käytetään biotinyloitua setuksimabi-(Erbitux®) vasta-ainetta, joka sitoutuu solujen yli-ilmentämiin EGF-reseptoreihin. Kaksivaiheista kohdennusta verrataan suoraan ja/tai passiiviseen kohdennukseen. Tehokkaampien kuvantamismenetelmien kehitys on vauhdittanut kohdennettujen nanopartikkelien tutkimusta. Isotooppikuvantamista käyttäen pystytään seuraamaan radioleiman jakautumista elimistössä ja kuvantamaan solutasolla tapahtuvia ilmiöitä. Kirjallisuuskatsauksessa perehdytään SPECT- ja PET-kuvantamiseen syövän hoidossa, sekä niiden hyödyntämiseen lääkekehityksessä nanopartikkelien kuvantamisessa. Kyseiset kuvantamismenetelmät erottuvat muista menetelmistä korkean erotuskyvyn, herkkyyden ja helppokäyttöisyyden suhteen. Kokeellisessa osassa 99mTc-leimattujen liposomien distribuutiota hiirissä tutkittiin SPECT-CT-laitteen avulla. Aktiivisuus kasvaimessa, pernassa ja maksassa kvantifioitiin InVivoScope-ohjelman ja gammalaskijan avulla. Tuloksia verrattiin keskenään. In vitro-kokeessa saavutettiin kaksivaiheisella kohdennuksella 2,7- 3,5-kertainen (solulinjasta riippuen) hakeutuminen soluihin kontrolliliposomeihin verrattuna. Kuitenkin suora kohdennus toimi kaksivaiheista kohdennusta paremmin in vitro. In vivo –kokeissa liposomit jakautuivat kasvaimeen tehokkaammin i.p.-annosteltuna kuin i.v.-annosteltuna. Kaksivaiheisella kohdennuksella saavutettiin 1,24-kertainen jakautuminen kasvaimeen (% ID/g kudosta) passiivisesti kohdennettuihin liposomeihin verrattuna. %ID/elin oli kohdennetuilla liposomeilla 5,9 % ja passiivisesti kohdennetuilla 5,4%. Todellinen ero oli siis pieni. InVivoScope:n ja gammalaskijan tulokset eivät korreloineet keskenään. Lisätutkimuksia ja menetelmän optimointia vaaditaan liposomien kohdennuksessa kasvaimeen.

A hypothesis on a specific sequence-dependent conformation of DNA and its relation to the binding of the lac-repressor protein

The structure and properties of the double-helical form of the alternating copolymer poly(dA-dT) are considered. Different lines of evidence are interpreted in terms of a structure in which every second phosphate-diester linkage has a conformation different from that of the normal B form. A rationale for this “alternating-B” structure is given which provides an explanation for the effects of chemical modifications of the T residues on the binding of the poly(dA-dT)· poly(dA-dT) to the lac repressor of Escherichia coli.

Miscibility of Poly(aromatic acrylate)s and Methacrylates with Styrene/Acrylonitrile copolymers

Miscibilities of some poly[aromatic (meth)acrylatels namely, poly(pheny1 acrylate) (PPA), poly(pheny1 methacrylate) (PPMA), poly(benzy1 acrylate) (PBA), and poly(benzy1 methacrylate) (PBMAY polystyrene blends, have been studied through the so-called copolymer effect by incorporating acrylonitrile units in PS chains. In these systems, miscibility occurs on account of the strong repulsion between the acrylonitrile and styrene units in the copolymer. PBA and PBMA were blended with different styreneacrylonitrile (SAN) copolymers. A miscibility window has been identified for the latter system, and from these limits, the binary interaction energy density parameters (B,j.’sw) ere calculated. Using these values, the miscibilities in other homopolymer-copolymer and copolymer-copolymer systems containing benzyl methacrylate, acrylonitrile, and styrene monomer units have been predicted and subsequently verified experimentally. The miscibility window limits in poly[aromatic (meth)acrylate]s/SAN copolymer blends have been compared. PBA does not exhibit a miscibility window with SAN copolymers, which has been explained by the weak intramolecular hydrogen bonding in PBA. The miscibility window in the PBW SAN copolymer system, as observed by DSC, shows a considerable narrowing in nonradiative energy transfer (NRET) measurements, as this technique is more sensitive.

Miscibility of poly(aromatic acrylate)s and methacrylates with styrene/acrylonitrile copolymers

Miscibilities of some poly[aromatic (meth)crylate]s namely, poly(phenyl acrylate) (PPA, poly(phenyl methacrylate) (PPMA), poly(benzyl acrylate) (PBA), and poly(benzyl methacrylate) (PBMA)/polystyrene blends, have been studied through the so-called copolymer effect by incorporating acrylonitrile units in PS chains. In these systems, miscibility occurs on account of the strong repulsion between the acrylonitrile and styrene units in the copolymer. PBA and PBMA were blended with different styrene-acrylonitrile (SAN) copolymers. A miscibility window has been identified for the latter system, and from these limits, the binary interaction energy density parameters (Bij's) were calculated. Using these values, the miscibilities in other homopolymer-copolymer and copolymer-copolymer systems containing benzyl methacrylate, acrylonitrile, and styrene monomer units have been predicted and subsequently verified experimentally. The miscibility window limits in poly[aromatic (meth)acrylate]s/SAN copolymer blends have been compared. PBA does not exhibit a miscibility window with SAN copolymers, which has been explained by the weak intramolecular hydrogen bonding in PBA. The miscibility window in the PBMA/SAN copolymer system, as observed by DSC, shows a considerable narrowing in nonradiative energy transfer (NRET) measurements, as this technique is more sensitive.

Vinyl Monomer Based Polyperoxides as Potential Initiators for Radical Polymerization: An Exploratory Investigation with Poly(.alpha.-methylstyrene peroxide)

We describe the use of poly(alpha-methylstyrene peroxide) (P alpha MSP), an alternating copolymer of alpha-methylstyrene and oxygen, as initiator for the radical polymerization of vinyl monomers. Thermal decomposition of P alpha MSP in 1,4-dioxane follows first-order kinetics with an activation energy (E(a)) of 34.6 kcal/mol. Polymerization of methyl methacrylate (MMA) and styrene using P alpha MSP as an initiator was carried out in the temperature range 60-90 degrees C. The kinetic order with respect to the initiator and the monomer was close to 0.5 and 1.0, respectively, for both monomers. The E(a) for the polymerization was 20.6 and 22.9 kcal/mol for MMA and styrene, respectively. The efficiency of P alpha MSP was found to be in the range 0.02-0.04. The low efficiency of P alpha MSP was explained in terms of the unimolecular decomposition of the alkoxy radicals which competes with primary radical initiation. The presence of peroxy segments in the main chain of PMMA and polystyrene was confirmed from spectroscopic and DSC studies. R(i)'/2I values for P alpha MSP compared to that of BPO at 80 degrees C indicate that P alpha MSP can be used as an effective high-temperature initiator.

A novel (main chain) (side chain) polymeric peroxide: Synthesis and initiating characteristics of poly(alpha-(tert-butylperoxymethyl)styrene peroxide)

A novel (main chain)-(side chain) vinyl polyperoxide, poly(alpha-(tert-butylperoxymethyl)styrene peroxide) (MCSCPP), an alternating copolymer of alpha-(tert-butylperoxymethyl)styrene (TPMS) and oxygen, has been synthesized by the oxidative polymerization of TPMS. The MCSCPP was characterized by H-1 NMR, C-13 NMR, IR, DSC, EI-MS, and GC-MS studies. The overall activation energy (E(a)) for the degradation of MCSCPP was found to be 27 kcal/mol. Formaldehyde and alpha-(tert-butylperoxy)acetophenone (TPAP) were identified as the primary degradation products of MCSCPP; TPAP was found to undergo further degradation. The side chain peroxy groups were found to be thermally more stable than those in the main chain. Polymerization of styrene in the presence of MCSCPP as initiator, at 80 degrees C, follows classical kinetics. The presence of peroxy segments in the polystyrene chain was confirmed by both H-1 NMR and thermal decomposition studies. Interestingly, unlike other vinyl polyperoxides, the MCSCPP initiator shows an increase in molecular weight with conversion.

Comparison of the miscibility strategies in poly(benzyl methacrylate)-polystyrene blends

Exothermic interactions like hydrogen bonding, ionic and charge transfer, etc., and ''copolymer effect'' are commonly used to induce miscibility in immiscible blends. The efficacy of these methods in promoting miscibility in poly(benzyl methacrylate) (PBMA)-polystyrene (PS) immiscible blends has been studied by suitably modifying the structure of the component polymers. It has been found that hydrogen bonding approach is most advantageous among these approaches as it involves the need for minimum interacting sites. It has also been shown that these results can be extended to the blends of poly(acrylate)s or poly(methacrylate)s with PS. (C) 1996 John Wiley & Sons, Inc.

A facile route to synthesize silver nanoparticles in polyelectrolyte capsules

We are reporting a novel green approach to incorporate silver nanoparticles (NPs) selectively in the polyelectrolyte capsule shell for remote opening of polyelectrolyte capsules. This approach involves in situ reduction of silver nitrate to silver NPs using PEG as a reducing agent (polyol reduction method). These nanostructured capsules were prepared via layer by layer (LbL) assembly of poly(allylamine hydrochloride) (PAH) and dextran sulfate (DS) on silica template followed by the synthesis of silver NPs and subsequently the dissolution of the silica core. The size of silver nanoparticles synthesized was 60 +/- 20 nm which increased to 100 +/- 20 nm when the concentration of AgNO3 increased from 25 mM to 50 mM. The incorporated silver NPs induced rupture and deformation of the capsules under laser irradiation. This method has advantages over other conventional methods involving chemical agents that are associated with cytotoxicity in biological applications such as drug delivery and catalysis. (C) 2011 Elsevier B.V. All rights reserved.

DNA Condensation by the Rat Spermatidal Protein TP2 Shows GC-Rich Sequence Preference and Is Zinc Dependent

Transition protein-2 (TP2), isolated from rat testes, was recently shown to be a zinc metalloprotein. We have now carried out a detailed analysis of the DNA condensing properties of TP2 with various polynucleotides using circular dichroism spectroscopy. The condensation of the alternating copolymers by TP2 (incubated with 10 mu M ZnSO4), namely, poly(dG-dC). poly(dG-dC) and poly(dA-dT). poly(dA-dT), was severalfold higher than condensation of either of the homoduplexes poly(dG). poly-(dC) and poly(dA). poly(dT) or rat oligonucleosomal DNA. Between the two alternating copolymers, poly(dG-dC). poly(dG-dC) was condensed 3.2-fold more effectively than poly(dA-dT). poly(dA-dT). Preincubation of TP2 with 5 mM EDTA significantly reduced its DNA-condensing property. Interestingly, condensation of the alternating copolymer poly(dI-dC). poly(dI-dC) by TP2 was much less as compared to that of poly(dG-dC). poly(dG-dC). The V8 protease-derived N-terminal fragment (88 aa) condensed poly(dA-dT). poly(dA-dT) to a very small extent but did not have any effect on poly(dG-dC). poly-(dG-dC). The C-terminal fragment (28 aa) was able to condense poly(dA-dT) . poly(dA-dT) more effectively than poly(dG-dC). poly(dG-dC). These results suggest that TP2 in its zinc-coordinated form condenses GC-rich polynucleotides much more effectively than other types of polynucleotides. Neither the N-terminal two-thirds of TP2 which is the zinc-binding domain nor the C-terminal basic domain are as effective as intact TP2 in bringing about condensation of DNA.