Scott Reeves - Academia.edu (original) (raw)

Papers by Scott Reeves

Silicon Chemistry, 2005

Two different methods for preparation of Cu 2+-poly(amidoamine-organosilicon) (PAMAMOS) dendrimer... more Two different methods for preparation of Cu 2+-poly(amidoamine-organosilicon) (PAMAMOS) dendrimer-based network nanocomplexes were developed and small angle neutron scattering (SANS) and X-ray photoelectron spectroscopy (XPS) were used for elucidation of fine structure of the obtained products. It was found that the in situ preparation method, by which less than the limiting amount of Cu 2+ for the given dendrimer generation was complexed with dissolved dendrimer before cross-linking, enabled precise templating of copper into the nanoscopic polyamidoamine (PAMAM) network domains only. The limiting amount of Cu 2+ for networks with generation 4 PAMAM domains was found to be between 5 (by SANS) and 8 (by XPS) mass %, in good agreement with the 9 mass % value calculated for idealized perfect dendrimer structure. It was also found that exceeding this concentration limit resulted in partitioning of Cu 2+ ions into the organosilicon (OS) network domains as well, probably because of possible complexation of cations with siloxane oxygens. Consistent with this, the diffusion method always resulted in random distribution of Cu 2+ cations throughout the bulk of the penetrated network layer(s), but the depth of this penetration was time-dependent and it followed Type II diffusion kinetics. This enables convenient control of layer thickness and preparation of thin layers of metal-network nanocomplexes. XPS data strongly suggest preferential Cu 2+-tert. N complexation with in the PAMAM network domains, and indicate an unexpected oxido-reduction process above a certain copper concentration (approximately 2 tert. N per Cu ion) that leads to the formation of Cu 1+ and N + species.

SPIE Proceedings, 2001

New acetal or ketal blocking reagents were investigated for use in e-beam lithography and compare... more New acetal or ketal blocking reagents were investigated for use in e-beam lithography and compared with the performance of ethyl vinyl ether (EVE). Three blocking groups, a-Angelicalactone (AL), 6-methylene-5,6-benzo-l,4-dioxane (MBD), and MANA50 (an undisclosed blocking group) were reacted with polyp-hydroxystyrene) (PHS) under acid catalyzed conditions to form AL-PHS, MBD-PHS, MANA50-PHS. The performance objectives pursued in the design of these new materials was to use acetal (ketal) chemistry to deliver wide process latitudes (e.g. good PED performance and minimal PEB sensitivity), use high molecular weight blocking groups to eliminate outgassing, and use the novel concept of multiple anions to deliver lithographic performance. These new materials are called Multiple Anion Nonvolatile Acetal (MANA) resists. Resists films were exposed with 50 kV electrons, post exposure baked (PEB), and developed with 0.26 N TMAH. Resists prepared with the third blocking group, MANA50, gave imaging performance independent of PEB humidity and were relatively insensitive to PEB temperature and post-exposure delay (PED). These resists gave the best resolution (90 nm) and profiles of all the materials tested, as well as showing very low outgassing and good etch resistance.

Macromolecules, 1999

Amphiphilic diblock copolymers were synthesized based on poly(2-ethyl-2-oxazoline) (PEtOz) as a h... more Amphiphilic diblock copolymers were synthesized based on poly(2-ethyl-2-oxazoline) (PEtOz) as a hydrophilic block and aliphatic polyesters such as poly(L-lactide) (PLA) or poly(-caprolactone) (PCL) as a hydrophobic block. Their micellar characteristics in an aqueous phase were investigated by using dynamic light scattering and fluorescence techniques. The block copolymers formed micelles in the aqueous phase with critical micelle concentrations (cmcs) in the range of 1.0-8.1 mg/L. The cmc values become lower upon increasing the length of the hydrophobic block. The mean diameters of the micelles were in the range of 108-192 nm, with a narrow distribution. In general, the micelle size increased as the hydrophobic PLA or PCL block became larger. The partition equilibrium constants, K v, of pyrene in the micellar solutions of the block copolymers were from 1.79 × 10 5 to 5.88 × 10 5. For each block copolymer system of PEtOz-PLA or PEtOz-PCL, the Kv value increased as the length of the hydrophobic block increased. The steady-state fluorescence anisotropy values (r) of 1,6-diphenyl-1,3,5-hexatriene (DPH) were 0.265-0.284 in PEtOz-PLA solution and 0.189-0.196 in PEtOz-PCL solution. The anisotropy values of PEtOz-PLAs were higher than those of PEtOz-PCLs. The anisotropy values were independent of the length of the hydrophobic block when the chemical structures of the hydrophobic blocks were identical. The micelles underwent hydrogen bonding at pH <3.5 with poly(acrylic acid), which produced polymer complex precipitates that could be reversibly dispersed as micelles at pH >3.8.

Macromolecules, 2002

Covalently cross-linked, three-dimensional nanodomained networks were prepared from radially laye... more Covalently cross-linked, three-dimensional nanodomained networks were prepared from radially layered poly(amidoamine-organosilicon) (PAMAMOS) copolymeric dendrimers containing hydrophilic polyamidoamine (PAMAM) interiors and reactive hydrophobic organosilicon (OS) exteriors. Two different types of curing chemistries were used, including (a) a sol-gel-type hydrolysis of alkoxysilylterminated dendrimers followed by a silanol condensation reaction and (b) irradiation or heat-induced, free-radical double-bond opening of vinylsilyl-or allylsilyl-terminated dendrimers, followed by free-radical coupling into carbosilane bridges. The first-mentioned process was investigated in more detail by monitoring the time-dependent weight loss, the glass transition temperatures (Tg), and the FT-IR spectroscopy of the resulting products. The effects of various coreagents, including acryloyldimethoxymethylsilane (DMOMS), tetraethoxysilane (TEOS) and R,ω-telechelic poly(dimethylsiloxane) disilanol (PDMS), on the structures and properties of the resulting networks, especially their T g's, were examined. It was found that, by varying the type of the PAMAMOS dendrimer network precursor, the type and relative amount of the coreagent, and the set of curing conditions used, different films, sheets, and coatings can be obtained. These were characterized by contact angle measurements, AFM, SEM, EDS, XPS, SANS, and SAXS analyses. The results obtained revealed smoothness at the nanoscopic level and low surface energy of these network materials and confirmed uniform distribution of well-defined hydrophilic PAMAM domains within the hydrophobic OS matrixes. Most importantly, sizes and shapes of these nanoscopic domains can be controlled by the selection of dendrimer network precursors and by conditions applied to the network formation.

Macromolecules, 1996

A new method for the synthesis of poly(dichlorophosphazene) at ambient temperatures is described.... more A new method for the synthesis of poly(dichlorophosphazene) at ambient temperatures is described. It involves the initiation of Cl3PdNSiMe3 with small amounts of PCl5 in CH2Cl2 to yield poly-(dichlorophosphazene), (NPCl2)n, with narrow polydispersities. The molecular weight of poly(dichlorophosphazene) was controlled by altering the ratio of monomer to initiator. The polymer chains were found to be active after chain propagation since further addition of monomer resulted in the formation of higher molecular weight polymer. Integration of 1 H and 31 P NMR spectra of these reactions revealed that the polymerization follows first-order reaction kinetics with respect to monomer concentration. Active polymer chains may be quenched or end-capped by the addition of trace quantities of Me2(CF3-CH2O)PdNSiMe3 or (CF3CH2O)3PdNSiMe3. Furthermore, PBr5, SbCl5, and Ph3C[PF6] were also found to be effective initiators in CH2Cl2 at room temperature.

ABSTRACT A new class of hydrophilic core – hydrophobic arms multi-arm star polymers is described:... more ABSTRACT A new class of hydrophilic core – hydrophobic arms multi-arm star polymers is described: the first such materials to have silicon located in the side arms. They belong to the broad family of radially layered copolymeric amidoamine-organosilicon (PAMAMOS) dendritic macromolecules and may be viewed as nanostructured, covalently bonded, inverse micelles. Two types of hydrophobic, silicon-containing arms have been used, one based on polydimethylsiloxane (PDMS) and another based on predominantly alkyl chains attached by organosilicon chemistry to the hydrophilic polyamidoamine (PAMAM) core. The former polymers are synthesized by a reaction of amine-terminated PAMAMs by mono-functional epoxy PDMS, while the latter are obtained by haloalkylation of the same PAMAMs with a suitable unsaturated silane followed by alkylthiol addition. The Langmuir film behavior of the multi-arm star polymers with PDMS arms is described and rationalized in comparison with that of other hydrophobically modified PAMAM dendrimers reported in the literature. Their uptake of Cu2+ from aqueous solutions is also described.

Macromolecules, 2000

ABSTRACT An advanced process for the synthesis of polyphosphazenes with controlled architectures ... more ABSTRACT An advanced process for the synthesis of polyphosphazenes with controlled architectures has been investigated. By this method, a wide range of well-defined phosphazene di- and triblock copolymers with controlled molecular weights and narrow polydispersities have been synthesized (Mn up to 4.8 × 104 with polydispersities of 1.06−1.39). The diblock copolymers, {[NPCl2]n[NPR(R‘)]m}, were synthesized by the cationic condensation polymerization of the phosphoranimines, PhCl2PNSiMe3, Me(Et)ClPNSiMe3, Me2ClPNSiMe3, Ph2ClPNSiMe3, and PhF2PNSiMe3, at 35 °C initiated from the “living” end unit of poly(dichlorophosphazene), [Cl−(PCl2N)n-PCl3+PCl6-] which was itself formed by the polymerization of Cl3PNSiMe3 with small amounts of PCl5 initiator in CH2Cl2 at 25 °C. Halogen replacement reactions through the use of NaOCH2CF3 and/or NaOCH2CH2OCH2CH2OCH3 on the diblock copolymers yielded fully organo-substituted macromolecules. In addition, the diblock copolymer {[NPMe(Et)]n[NPMe(Ph)]m} was formed by the block copolymerization of the two different organophosphoranimines. Triblock species were produced by the reaction of the “living” difunctional initiator, −{CH2NH(CF3CH2O)2P−N−PCl3+PCl6-}2, first with Cl3PNSiMe3 and second with Me(Et)ClPNSiMe3, followed by halogen replacement with NaOCH2CF3, to yield the triblock {[(Et)MePN]m[(CF3CH2O)2PN]n−P(OCH2CF3)2NHCH2CH2NH−(CF3CH2O)2P−[NP(OCH2CF3)2]n[NPMe(Et)]m}. The evidence for the formation of the di- and triblock copolymers includes NMR, GPC, elemental analysis, and solubility data.

…, 1997

... opposite polarity to that found for 2, and this is indirect evidence that the product is a co... more ... opposite polarity to that found for 2, and this is indirect evidence that the product is a copolymer rather than two separate ... To obtain higher conversions of 6 to polymer, monomer 6 was treated with a more concentrated solution of (N PCl 2 ... 1) Honeyman, CH; Manners, I.; Morrissey ...

Macromolecules, 2001

... Harry R. Allcock,* Scott D. Reeves, Christine R. de Denus, and Chester A. Crane. Department o... more ... Harry R. Allcock,* Scott D. Reeves, Christine R. de Denus, and Chester A. Crane. Department of Chemistry, The Pennsylvania State University, 152 Davey Laboratory, University Park, Pennsylvania 16802. Macromolecules , 2001, 34 (4), pp 748–754. ...