Search results for "Condensation"

Fluorescence microscopy studies of layer/substrate interaction during the Langmuir-Blodgett transfer: Fractional condensation and local layer modific…

1991

Transfer fluorescence microscopy reveals the substrate-mediated fractional condensation and phase-selective deposition of dipalmitoylphosphatidylcholine (DPPC) and dimyristoylphosphatidylethanolamine (DMPE) monolayers during the LB-transfer. Preferentially the higher ordered liquid-condensed (LC) state is transferred onto the substrate during the transfer of a monolayer in the LC/LE (liquid/expanded) coexistence state on the water subphase. This is manifested in the directly observable attraction of LC-domains towards the three-phase line and observation of a domain-free gap as consequence of the segregation of the fluorescent probe into the floating monolayer adjacent to the three-phase li…

Thermodynamic and Neutron-Diffraction Studies of H2 and D2 Multilayers Physisorbed on Graphite

1991

The evolution of physisorbed films from two-dimensional (2D) to bulk behavior is a topic of high current interest.1 In this context the behavior of the quantum systems H2, HD and D2 is of particular relevance because of the following reasons: 1. Due to the strong influence of the quantum zero-point energy the hydrogen isotopes are highly compressible. This leads to strongly compressed monolayers2,3 before further layer condensation occurs. This property makes these systems significant for the exploration of conditions of multilayer growth. It is generally believed,1,4–6 that the incompatibility between the adsorbate and bulk lattice structures gives rise to lateral strains between the overl…

2013

Abstract. As part of the CLACE-6 campaign we performed size-resolved CCN measurements for a~supersaturation range of S = 0.079 % to 0.66% at the high-alpine research station Jungfraujoch, Switzerland, in March~2007. The derived effective hygroscopicity parameter κ describing the influence of particle composition on CCN activity was on average 0.23–0.30 for Aitken (50–100 nm) and 0.32–0.43 for accumulation mode particles (100–200 nm). The campaign average value of κ = 0.3 is similar to the average value of κ for other continental locations. When air masses came from southeasterly directions crossing the Po Valley in Italy, particles were much more hygroscopic (κ ≈ 0.42) due to…

Site-selectivity control in hetero-Diels-Alder reactions of methylidene derivatives of lawsone through modification of the reactive carbonyl group: a…

2019

A new perspective on the reactivity of hydroxyquinones was revealed as an acetal derivative of lawsone was synthesized, isolated, and used in tandem Knoevenagel/hetero-Diels-Alder reactions catalyzed by S-proline. The intermediate alkylidene-1,3-diones that were formed in situ reacted with electron rich alkenes to predominantly afford pyrano-1,2-naphthoquinone (β-lapachone) derivatives along with the isomeric pyrano-1,4-naphthoquinone (α-lapachone) derivatives in high to excellent total yields. Interestingly, the highly reactive arylidene-1,3-dione derivatives were found to be stable and isolable. DFT calculations suggest that these hetero-Diels-Alder reactions have a high polar character, …

Oligo(ether sulfones). 3. Block Copolymers via Condensation Reactions of Telechelic Oligo(ether sulfones) Bearing Phenolic Endgroups and Oligomeric α…

1999

Synthesis of Reactive Telechelic Polymers Based on Pentafluorophenyl Esters

2008

A diazo initiator and a chain transfer agent (CTA), both containing a pentafluorophenyl (PFP) activated ester, were synthesized. In a RAFT polymerization using the functionalized chain transfer agent (PFPCTA), methyl methacrylate (MMA), diethylene glycol monomethyl ether methacrylate (DEGMA), poly(ethylene glycol) monomethyl ether methacrylate (PEGMA), and lauryl methacrylate (LMA) could successfully be polymerized into homopolymers and diblock copolymers with good control over molecular weight, very high conversions, and narrow molecular weight distributions. Polymers derived from the PFP-CTA possessed an activated ester at the R-end of the polymer chain, which could be reacted with amines…

Metalation and N-alkylation of some polyamides

1981

Totally N-substituted polyamides were synthesized starting from poly(2,4,4-trimethylhexamethylene terephthalamide) by metalation of the amide groups and subsequent reaction with several electrophiles. Polyamides of this structure are not available from terephthalic acid and the corresponding diamines by polycondensation. This N-alkylation reaction can be used for the synthesis of comb-like graft copolymers. The solubilitity and the thermal properties of these polyamide derivatives are described.

Microcanonical Determination of the Interface Tension of Flat and Curved Interfaces from Monte Carlo Simulations

2012

The investigation of phase coexistence in systems with multi-component order parameters in finite systems is discussed, and as a generic example, Monte Carlo simulations of the two-dimensional q-state Potts model (q=30) on LxL square lattices (40<=L<=100) are presented. It is shown that the microcanonical ensemble is well-suited both to find the precise location of the first order phase transition and to obtain an accurate estimate for the interfacial free energy between coexisting ordered and disordered phases. For this purpose, a microcanonical version of the heatbath algorithm is implemented. The finite size behaviour of the loop in the curve describing the inverse temperature vers…

Straightforward preparation of highly loaded MWCNT-polyamine hybrids and their application in catalysis

2020

Multiwalled carbon nanotubes (MWCNTs) were easily and efficiently functionalised with highly cross-linked polyamines. The radical polymerisation of two bis-vinylimidazolium salts in the presence of pristine MWCNTs and azobisisobutyronitrile (AIBN) as a radical initiator led to the formation of materials with a high functionalisation degree. The subsequent treatment with sodium borohydride gave rise to the reduction of imidazolium moieties with the concomitant formation of secondary and tertiary amino groups. The obtained materials were characterised by thermogravimetric analysis (TGA), elemental analysis, solid state 13C-NMR, Fourier-transform infrared spectroscopy (FT-IR), transmission ele…

Synthesis and characterization of polyene chromophores with hydroxyl functionalization

2008

Abstract Eight hydroxyl functionalized donor–acceptor polyene chromophores 3–10 were synthesized and characterized. Knoevenagel condensation reaction of aromatic polyenals with 2-cyanoacetamide derivatives was utilized to synthesize chromophores with all-E configuration. Chromophores of this kind can be attached covalently to polymers or functionalized with dendrons in order to tune the properties. The structures of the molecules were verified by 1H NMR, 13C NMR, ESI-TOF mass spectrometry and UV–vis measurements. Reduced bond-length alternation of the molecules in DMSO-d6 solution were observed by calculating the average difference of the vicinal coupling constants between adjacent CH CH an…