No abstract

For ultrahigh-density storage media and D-RAM, the feature size of lithography should be much reduced (say less than 10 nm). Though some research groups reported feature size of 5–6 nm, further reduced feature size is needed for next-generation lithography. We synthesized, via a reversible addition–fragmentation chain-transfer polymerization, polydihydroxystyrene-block-polystyrene (PDHS-b-PS) copolymers showing lamellar and cylindrical microdomains by adjusting the volume fraction of PS block (f PS). We found that the Flory–Huggins interaction parameter (χ) between PDHS and PS was very large, 0.7 at 170 °C. Because of the huge χ, the lamellar domain spacing (L) of PDHS-b-PS with a total molecular weight of 2.1 kg mol–1 and f PS = 0.5 was only 5.9 nm; thus, a sub-3 nm feature size (half-pitch) was successfully obtained. Furthermore, PDHS-b-PS with a molecular weight of 4.2 kg mol–1 and f PS = 0.79 showed hexagonally packed cylinders with 4 nm diameter. We also obtained thin films of PDHS-b-PS with cylindrical microdomains, showing 8.8 nm center-to-center spacing. Furthermore, we fabricated ultrahigh-density ZrO2 nanowire arrays from the cylindrical monolayer thin films via atomic layer deposition, indicating an applicability of PDHS-b-PS for next-generation lithography.

No abstract

Well-defined amphiphilic poly(ε-caprolactone)-b-poly(N-vinylpyrrolidone) (PCL-b-PNVP) block copolymers were successfully prepared via the combination of ring-opening polymerization (ROP) and xanthate-mediated reversible additionÀfragmentation chain transfer (RAFT) polymerization. Well-defined poly(ε-caprolactone) (PCLÀOH) was synthesized by ROP in bulk at 110 °C using benzyl alcohol as initiator and stannous octate [Sn(Oct) 2 ] as catalyst . The ÀOH end group was then converted into its corresponding xanthate (PCLÀX) via the conversion to its corresponding bromide (PCLÀBr). These are verified by 1 H NMR spectroscopy. PCL-b-PNVP block copolymers were synthesized via RAFT polymerization in tetrahydrofuran (THF) at 80 °C using PCLÀX as macro-chain transfer agent and characterized by 1 H NMR spectroscopy and gel permeation chromatography (GPC). The amphiphilic diblock copolymer PCL 63 -b-PNVP 90 forms spherical micelles of ∼34 nm diameter in water as shown by transmission electron microscopy (TEM), supported by 1 H NMR spectroscopy, and light scattering. The critical micellar concentrations were determined by fluorescence spectroscopy using pyrene as probe. The critical micelle concentration (cmc) value of the block copolymers increases with the increase in the chain length of PNVP block. The overall hydrodynamic radius (R h ) of the micelles remains almost constant over the concentration range above the cmc value and over the angles of scattering measurement.

BackgroundThe present study was motivated by the need to design a safe nano-carrier for the delivery of doxorubicin which could be tolerant to normal cells. PCL63-b-PNVP90 was loaded with doxorubicin (6 mg/ml), and with 49.8% drug loading efficiency; it offers a unique platform providing selective immune responses against lymphoma.MethodsIn this study, we have used micelles of amphiphilic PCL63-b-PNVP90 block copolymer as nano-carrier for controlled release of doxorubicin (DOX). DOX is physically entrapped and stabilized in the hydrophobic cores of the micelles and biological roles of these micelles were evaluated in lymphoma.ResultsDOX loaded PCL63-b-PNVP90 block copolymer micelles (DOX-PCL63-b-PNVP90) shows enhanced growth inhibition and cytotoxicity against human (K-562, JE6.1 and Raji) and mice lymphoma cells (Dalton's lymphoma, DL). DOX-PCL63-b-PNVP90 demonstrates higher levels of tumoricidal effect against DOX-resistant tumor cells compared to free DOX. DOX-PCL63-b-PNVP90 demonstrated effective drug loading and a pH-responsive drug release character besides exhibiting sustained drug release performance in in-vitro and intracellular drug release experiments.ConclusionUnlike free DOX, DOX-PCL63-b-PNVP90 does not show cytotoxicity against normal cells. DOX-PCL63-b-PNVP90 prolonged the survival of tumor (DL) bearing mice by enhancing the apoptosis of the tumor cells in targeted organs like liver and spleen.