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Bottlebrushes with controlled horizontal‐ and vertical‐axis scales, which have a high density of graft chains on their main chains, are useful as a nanomaterial. The properties of bottlebrushes depend on the polymer‐type, ‐chain length, and grafting density. We fabricate well‐defined bottlebrushes based on poly(2‐hydroxyethyl methacrylate) (PHEMA) using the grafting from method. Macroinitiators with different compositions of an atom transfer radical polymerization (ATRP) initiator group are prepared, and two bottlebrushes are consequently synthesized by ATRP of HEMA with the macroinitiator: a concentrated bottlebrush with graft chains on the repeating units and a semi‐dilute bottlebrush with graft chains on approximately 10%. The hydrodynamic and gyration radii of the concentrated‐ and semi‐dilute bottlebrushes are Rh = 9.2 nm (Rg = 24.9 nm) and Rh = 69.1 nm (Rg = 130 nm), respectively. The shape factors (Rg/Rh) of these bottlebrushes indicate both solid‐rods. The virial coefficient of semi‐dilute bottlebrush, calculated from static light scattering measurements, is higher than that of concentrated bottlebrush, owing to the flexibility and solvation structure. The grafting density play a more prominent role than the graft‐chain length in the excluded volume effect of the bottlebrush. These results provide useful insights for the construction of polymethacrylate‐based bottlebrushes with specific hydrodynamic properties. [ABSTRACT FROM AUTHOR]

A series of glucose‐based degradable superabsorbent hydrogels with potential to tackle issues associated with sustainability, flooding, and drought has been designed and fabricated. These hydrophilic networks were constructed through integrating glucose as a primary building block –into cyclic oligomers and block polymers, which were combined into mechanically‐interlocked slide‐ring crosslinked materials. Crosslinking of slide ring α‐cyclodextrin/poly(ethylene glycol)‐type polyrotaxanes with acid‐functionalized ABA triblock copolymers comprised of mercaptopropionic acid‐functionalized poly(glucose carbonate (ethyl propargyl carbonate))‐b‐poly(ethylene glycol)‐b‐mercaptopropionic acid‐functionalized poly(glucose carbonate (ethyl propargyl carbonate)), afforded degradable superabsorbent hydrogels through establishment of chemically‐labile ester linkages, in addition to glycosidic and carbonate groups of the polymer precursors. With an emphasis on development of fundamental synthetic design strategies to achieve high‐performance superabsorbent hydrogels that could behave as robust materials, which are derived from natural components and exhibit hydrolytic degradability, effort went into optimization of the composition, structure, and topology leading to water uptake capacities >30× by mass. Investigations of composition‐structure‐topology‐morphology effects on properties as a function of variations of PEG main chain length, degree of α‐cyclodextrin coverage, and concentration of pre‐gel solution, indicated that the slide‐ring polymer and triblock copolymer networks feature high water uptake, tunable mechanical properties, and sustainability with construction from renewable natural products and in‐built degradability. [ABSTRACT FROM AUTHOR]

Polyunsaturated fatty acids (PUFAs) such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are essential fatty acids. PUFA synthases are composed of three to four subunits and each create a specific PUFA without undesirable byproducts. However, detailed biosynthetic mechanisms for controlling final product profiles have been obscure. Here, the bacterial DHA and EPA synthases were carefully dissected by in vivo and in vitro experiments. In vitro analysis with two KS domains (KSA and KSC) and acyl‐acyl carrier protein (ACP) substrates showed that KSA accepted short‐ to medium‐chain substrates while KSC accepted medium‐ to long‐chain substrates. Unexpectedly, condensation from C18 to C20, the last elongation step in EPA biosynthesis, was catalyzed by KSA domains in both EPA and DHA synthases. Conversely, condensation from C20 to C22, the last elongation step for DHA biosynthesis, was catalyzed by the KSC domain in DHA synthase. KSC domains therefore determine the chain lengths. [ABSTRACT FROM AUTHOR]

11h is a very potent inhibitor against epidermal growth factor receptor triple mutation L858R/T790M/C797S (EGFRTM) with 13‐fold stronger potency than the FDA‐approved osimertinib. Recently, two new EGFRTM inhibitors, 11d and 11e, were reported which revealed 2.8‐ and 2.3‐fold stronger potency than 11h, respectively. 11h, 11d, and 11e have the same structures but differ only in their aliphatic chain length. However, the exact effects of differential aliphatic chain length on the inhibitory potencies of these compounds require further elaboration at the atomistic level, hence the objective of this report. Various computational tools were employed for this purpose. From our findings, it was revealed that van der Waals (vdW) interactions modulate the binding mechanisms of these inhibitors and play the most important role in the differential inhibitory activities of 11d, 11h, and 11e. The strong hydrogen bond formation between the aliphatic chain of 11d and key residue ARG841 was recognized as the reason for its higher activity and inhibitory potency relative to 11h and 11e. Moreover, the extension of the N‐terminal loop into the active site for vdW interaction with the phenyl group of 11e and carbon–hydrogen bond formed between the aliphatic chain of 11e and LEU718 engendered a higher activity of 11e than 11h. [ABSTRACT FROM AUTHOR]

To meet the demands of a competitive market, an industrial plant often produces several grades of polymer product through the same process in an economical way. As molecular weight distribution (MWD) is a crucial quality index of polymers, dynamic optimization for grade transition based on MWD is highly important, but challenging. This study considers the development of optimization models for MWD‐based grade transition. An MWD reconstruction method using orthogonal collocation in two dimensions is developed to capture the dynamic feature of MWD in time and the distributive feature in chain length. The simultaneous collocation approach is adopted to discretize the model. Two optimization formulations are proposed to describe minimizing the transition time as well as off‐spec production. Both formulations inherit the advantages of the simultaneous collocation approach. The numerical results show that the proposed methods can efficiently solve the grade transition problem with MWD specification, and obtain high performance control profiles to reduce the production cost. © 2019 American Institute of Chemical Engineers AIChE J, 65: 1198–1210, 2019 [ABSTRACT FROM AUTHOR]

In this study, using hexamethylenediamine (HMD)‐modified magnetic graphene oxide (HMGO‐NH2) as carrier, HMD and methyl acrylate as function monomers, MGO grafted with longer hydrophobic chain length low‐generation HMD type polyamidoamine dendrimers (HMGO‐PAMAM‐G1.0) was prepared by Michael addition and amidation condensation reaction. The obtained HMGO‐PAMAM‐G1.0 sample was characterized by transmission electron microscope, X‐ray diffraction, Fourier transform infrared spectroscopy, nitrogen adsorption/desorption isotherms, thermal properties analysis, vibrating sample magnetometer, and X‐ray photoelectron spectroscopy analysis. The adsorption properties for Pb(II) and Hg(II) heavy metal ions of HMGO‐PAMAM‐G1.0 and the magnetic graphene oxide grafted with shorter hydrophobic chain length low‐generation ethylenediamine type polyamidoamine dendrimers (MGO‐PAMAM‐G1.0) reported in our previous work were explored. The results showed that the HMGO‐PAMAM‐G1.0 with longer hydrophobic chain length had higher adsorption capacity for Pb(II) and Hg(II) than MGO‐PAMAM‐G1.0 at the higher concentrations. The adsorption process of HMGO‐PAMAM‐G1.0 and MGO‐PAMAM‐G1.0 for Pb(II) and Hg(II) was well in agreement with pseudo‐second‐order kinetic model and the Langmuir isotherm model. The Pb(II) was only adsorbed on the sample, while the Hg(II) was partially reduced to Hg(I) in the adsorption process. POLYM. COMPOS., 40:E1685–E1696, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

We present a molecular dynamics simulation study of the probe diffusion and friction dynamics of Lennard-Jones particles in a series of liquid n-alkane systems from C12 up to C400 at 318 K, 418 K, 518 K, and 618 K, to investigate the power law dependence of self-diffusion of polymer liquids on their molecular weights. Two LJ particles MY1 with a mass of 114 g/mol and MY2 with a mass of 225 g/mol are used as probes to model methyl yellow. We observed that a clear transition in the power law dependence of n-alkane self-diffusion on the molecular weight (M) of n-alkane, Dself∼M−γ, occurs in the range C120∼C160 at temperatures of 318 K, 418 K, and 518 K, corresponding to a crossover from the "oligomer" to the "Rouse" regime. We also observed that a clear transition in the power law dependence of the diffusion coefficient DMY2 on the molecular weight (M) of n-alkane, DMY2∼M−γ, occurs at low temperatures. The exponent γ for DMY2 shows a sharp transition from 1.21 to 0.52 near C36 at 418 K and from 1.54 to 0.60 near C36 at 318 K. However, no such transition is found for the probe molecule MY2 at temperatures of 518 K and 618 K and for MY1 probe at temperatures of 418 K, 518 K, and 618 K, but the power law exponent γ for MY1 at 318 K shows instead a linear or a rather slow transition. The dependence of the probe diffusion (DMY2) on the matrix molecular weight (M) reflects a significant change of the matrix dynamics associated with the probe diffusion: a crossover from the "solvent-like" to the "oligomer" regime. As the molecular weight of n-alkane increases, the ratio of Dself/DMY2 becomes less than 1 and the probe molecules encounter, in turn, two different microscopic frictions depending on MMY/Mmatrix and the temperature. It is believed that a reduction in the microscopic friction on the probe molecules that diffuse at a rate faster than the solvent fluctuations leads to large deviations of slope from the linear dependence of the friction of MY2 on the chain length of the n-alkane at 318 K and 418 K. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the effects of rice variety, water content, and preparation temperature on the textural properties of gels processed from cooked rice grains via high‐speed shear homogenization. Rice gels were prepared from seven high‐amylose rice varieties. The results demonstrated the significant differences in rice gel hardness and hardening rates during storage based on the rice variety used. The proportion of short chains of amylopectin was negatively correlated with the hardness of the rice gel. The sample temperature before shear treatment also influenced the rice gel hardness. Rice gels prepared from cooked rice maintained at 75°C prior to homogenization showed a higher breaking force than those from cooked rice at 25°C. Observation using scanning electron microscopy demonstrated the tendency of the cooked rice sample maintained at 75°C to form a finer gel network after homogenization than those at 25°C from the same rice variety. The objective of this study was to investigate the effects of rice variety, water content, and preparation temperature on the textural properties of gels processed from cooked rice grains via high‐speed shear homogenization. The starch characteristics of each rice variety were reflected in the differences in rice gel hardness. In addition, the gel network formed in the process of high‐speed shear homogenization had a considerable impact on gel hardness. [ABSTRACT FROM AUTHOR]

A growing number of approaches to "staple" α‐helical peptides into a bioactive conformation using cysteine cross‐linking are emerging. Here, the replacement of l‐cysteine with "cysteine analogues" in combinations of different stereochemistry, side chain length and beta‐carbon substitution, is explored to examine the influence that the thiol‐containing residue(s) has on target protein binding affinity in a well‐explored model system, p53–MDM2/MDMX, which is constituted by the interaction of the tumour suppressor protein p53 and proteins MDM2 and MDMX, which regulate p53 activity. In some cases, replacement of one or more l‐cysteine residues afforded significant changes in the measured binding affinity and target selectivity of the peptide. Computationally constructed homology models indicate that some modifications, such as incorporating two d‐cysteine residues, favourably alter the positions of key functional amino acid side chains, which is likely to cause changes in binding affinity, in agreement with measured surface plasmon resonance data. Cysteine‐editing: Stapled peptides can be prepared by cysteine cross‐linking with hexafluorobenzene. Replacement of one or more l‐cysteine residues with "cysteine analogues" changes both the peptide target affinity and selectivity for proteins MDM2/MDMX as demonstrated by surface plasmon resonance measurements. [ABSTRACT FROM AUTHOR]

We have observed the inversion of the solvation environment of a one‐dimensional solid by low‐temperature scanning tunneling microscopy. Adsorption of 3‐methoxy‐9‐diazofluorene on Ag(111) yields highly oriented supramolecular chains, which are then exposed to water molecules. The annealing of dry and water‐decorated chains results in diametrically opposed outcomes. While the former simply leads to an increase in chain length and number, the latter results in a complete loss of order and produces water clusters decorated with the organic molecule. The formation of a one‐dimensional solid, its hydration, and its dissolution on a Ag(111) surface were followed by low‐temperature scanning tunneling microscopy. The annealing of dry chains results in a simple increase in chain length and number whereas the annealing of water‐decorated chains results in a complete loss of order and produces water clusters decorated with the organic molecule. [ABSTRACT FROM AUTHOR]

A new way is presented to prepare group 14 compounds substituted with a terminal NHC stabilized phosphenidenyl substituent. On this occasion, it is shown that depending on the chain length of the group 14 element dichlorides in reaction with SIMesPK a mono‐ or disubstitution can be observed. Starting from Me2SiCl2 or tBu2SnCl2 a single substitution occurred. Longer chains of group 14 dihalides like (SiMe2Cl)2 or O(SiMe2SiMe2Cl)2 lead to silicon bridged bisphosphinidenyl compounds. [ABSTRACT FROM AUTHOR]

ABSTRACT: Two donor‐π‐acceptor (D‐π‐A) type naphtho[1,2‐c:5,6‐c′]bis[1,2,5]thiadiazole (NT)‐based conjugated copolymers (CPs), namely, PBDT‐TT‐DTNT‐HD and PBDT‐TT‐DTNT‐OD, containing different side chain length (2‐hexyldecyl, HD and 2‐octyldodecyl, OD) anchoring to thiophene π‐bridge between the two‐dimensional (2D) 5‐((2‐butyloctyl)thieno[3,2‐b]thiophen‐2‐yl)benzo[1,2‐b:4,5‐b′]dithiophene (BDT‐TT) unit and NT moiety are developed and fully characterized. The resultant two copolymers exhibited broader absorption in wide range of 300–820 nm and obviously deepened EHOMO of approximately −5.50 eV. The effects of side chain length on film‐forming ability, absorption, energy levels, aggregation, dielectric constant (ɛr), mobility, morphology, and photovoltaic properties are further systematically investigated. It was found that the side chain length had little impact on solution‐processability, absorption, energy levels, and aggregation in CB solution of resultant CPs. However, tinily increasing side chain length promoted to form the more ordered structure of neat polymer film even if the corresponding ɛr decreased. As a result, the side‐chain‐extended PBDT‐TT‐DTNT‐OD:PC71BM‐based device achieved 32% increased FF than that of PBDT‐TT‐DTNT‐HD:PC71BM and thus the PCE was significantly raised from 3.99% to 5.21%, which were benefited from 2 times higher SCLC hole mobility, more favorable phase separation, and improved exciton dissociation. These findings could provide an important and valuable insight by side chain modulation for achieving efficient PSCs. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 2059–2071 [ABSTRACT FROM AUTHOR]

ABSTRACT: Charge transport in conjugated polymers may be governed not only by the static microstructure but also fluctuations of backbone segments. Using molecular dynamics simulations, we predict the role of side chains in the backbone dynamics for regiorandom poly(3‐alkylthiophene‐2,5‐diyl)s (P3ATs). We show that the backbone of poly(3‐dodecylthiophene‐2‐5‐diyl) (P3DDT) moves faster than that of poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) as a result of the faster motion of the longer side chains. To verify our predictions, we investigated the structures and dynamics of regiorandom P3ATs with neutron scattering and solid state NMR. Measurements of spin‐lattice relaxations (T1) using NMR support our prediction of faster motion for side chain atoms that are farther away from the backbone. Using small‐angle neutron scattering (SANS), we confirmed that regiorandom P3ATs are amorphous at about 300 K, although microphase separation between the side chains and backbones is apparent. Furthermore, quasi‐elastic neutron scattering (QENS) reveals that thiophene backbone motion is enhanced as the side chain length increases from hexyl to dodecyl. The faster motion of longer side chains leads to faster backbone dynamics, which in turn may affect charge transport for conjugated polymers. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 1193–1202 [ABSTRACT FROM AUTHOR]

Abstract: Cationic polylysine promotes, under neutral conditions, the spontaneous aggregation of opposite charged ZnTPPS in water. Spectroscopic investigations evidence a different preorganization of ZnTPPS onto the polypeptide matrix depending on the chain length. Spinodal decomposition theory in confined geometry is used to model this mechanism by considering the time evolution of a homogeneous distribution of randomly adsorbed particles (porphyrins) onto a rodlike polyelectrolyte (polymer) of variable length L. [ABSTRACT FROM AUTHOR]

Abstract: Membrane‐intercalating conjugated oligoelectrolytes (COEs) are emerging as potential alternatives to conventional, yet increasingly ineffective, antibiotics. Three readily accessible COEs, belonging to an unreported series containing a stilbene core, namely D4, D6, and D8, were designed and synthesized so that the hydrophobicity increases with increasing side‐chain length. Decreased aqueous solubility correlates with increased uptake by E. coli. The minimum inhibitory concentration (MIC) of D8 is 4 μg mL−1 against both E. coli and E. faecalis, with an effective uptake of 72 %. In contrast, the MIC value of the shortest COE, D4, is 128 μg mL−1 owing to the low cellular uptake of 3 %. These findings demonstrate the application of rational design to generate efficacious antimicrobial COEs that have potential as low‐cost antimicrobial agents. [ABSTRACT FROM AUTHOR]

Abstract: Bonding is a fundamental aspect of organic chemistry, yet the magnitude of C=C bonding in [n]cumulenes as a function of increasing chain length has yet to be experimentally verified for derivatives longer than n=5. The synthesis of a series of apolar and unsymmetrically substituted tetraaryl[n]cumulenes (n=3, 5, 7, 9) was developed and rotational barriers for Z/E isomerization were measured using dynamic VTNMR spectroscopy. Both experiment and theory confirm a dramatic reduction in the rotational barrier (through estimation of ΔG≠rot for the isomerization) across the series, from >24 to 19 to 15 to 11 kcal−1 in [n]cumulenes with n=3, 5, 7, 9, respectively. The reduction in cumulenic bonding in longer cumulenes thus affords bond rotational barriers that are more characteristic of a sterically hindered single bond than that of a double bond. [ABSTRACT FROM AUTHOR]

Abstract: Polymer‐grafted magnetic nanoparticles at oil–air interfaces are examined to reveal the role of chain length and anisotropy on particle packing order in thin films. It is found that particles grafted with intermediate chain lengths and sparse grafting densities exhibit enhanced packing order with increasing magnetic field strength. Voronoi tessellation results present an increase in the cell area distribution of these samples, suggesting that chain conformations are affected. For the longest graft length, particles become more disordered under magnetic fields. It is proposed that fluctuations in the bridged chains rearrange particles into less ordered packing with field application and the mechanism of packing order differs for varying graft chain lengths. Grafting anisotropy is found to determine the spatial nanoparticle organization in assembled monolayers. [ABSTRACT FROM AUTHOR]

ABSTRACT: This work reports the synthesis of novel poly(3′,4′‐bis(alkyloxy)terthiophene) derivatives (PTTOBu, PTTOHex, and PTTOOct) and their supercapacitor applications as redox‐active electrodes. The terthiophene‐based conducting polymers have been derivatized with different alkyl pendant groups (butyl‐, hexyl‐, and octyl‐) to explore the effect of alkyl chain length on the surface morphologies and pseudocapacitive properties. The electrochemical performance tests have revealed that the length of alkyl substituent created a remarkable impact over the surface morphologies and charge storage properties of polymer electrodes. PTTOBu, PTTOHex, and PTTOOct‐based electrodes have reached up to specific capacitances of 94.3, 227.3, and 443 F g−1 at 2.5 mA cm−2 constant current density, respectively, in a three‐electrode configuration. Besides, these redox‐active electrodes have delivered satisfactory energy densities of 13.5, 29.3, and 60.7 W h kg−1 and power densities of 0.98, 1, and 1.1 kW kg−1 with good capacitance retentions after 10,000 charge/discharge cycles in symmetric solid‐state micro‐supercapacitor devices. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 480–495 [ABSTRACT FROM AUTHOR]

Abstract: While type II polyketide synthases (PKSs) are known for producing aromatic compounds, a phylogenetically new subfamily of type II PKSs have been recently proposed to synthesize polyene structures. Here we report in vitro analysis of such a type II PKS, IgaPKS for ishigamide biosynthesis. The ketoreductase (Iga13) and dehydratase (Iga16) were shown to catalyze the reduction of a β‐keto group and dehydration of a β‐hydroxy group, respectively, to form a trans double bond. Incubation of the acyl carrier protein (Iga10), the ketosynthase/chain length factor complex (Iga11–Iga12), Iga13 and Iga16 with malonyl and hexanoyl‐CoAs and NADPH followed by KOH hydrolysis resulted in the formation of four unsaturated carboxylic acids (C8, C10, C12, and C14), indicating that IgaPKS catalyzes tetraene formation by repeating the cycle of condensation, keto‐reduction and dehydration with strict stereo‐specificity. We propose “highly reducing type II PKS subfamily” for the polyene‐producing type II PKSs. [ABSTRACT FROM AUTHOR]

Abstract: For effective application of nanoparticles, their amenability to in‐solution processing must be addressed, and stable, homogeneous solvent conditions are required. Although organic ligands have been used as surface‐modifying reagents for nanoparticles to increase their colloidal stability and homogeneity in solution, the structure–function relationships of nanoparticle–ligand complexes remain elusive and controversial. Herein, a series of novel amphiphilic small‐molecule ligands were designed, synthesized, and applied as surface‐modifying reagents for aqueous, transparent TiO2 and ZrO2 nanoparticles. The colloidal stability of the resulting nanoparticle–ligand complexes was found to depend not only on the chain length, but also on the relative balance between hydrophobicity and hydrophilicity. The structure of the ligands can be fine‐tuned to achieve “flexible colloidal stability”, thus significantly increasing complex stability in a variety of organic solvents. [ABSTRACT FROM AUTHOR]

An efficient biosensor was created for the ratiometric monitoring of Cu+ and pH in the brain using both current and potential outputs. A series of N, N-bis(2-[2-(ethylthio)ethyl])-based (NS4s) derivatives was designed for the specific recognition of Cu+. After systematically evaluating the electrochemical parameters of Cu+ oxidation by tuning alkyl chain length, polyaromatic structure, and substitute group site of NS4, N, N-bis(2-[2-(ethylthio)ethyl])-2-naphthamide (NS4-C1) was finally optimized for Cu+ detection as it showed the most negative potential and the largest current density. At the same time, 9,10-anthraquinone was used as a selective pH sensor with 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) as an internal reference. This single biosensor with both current and potential signal outputs can simultaneously determine Cu+ concentrations from 0.5 to 9.5 μ m and pH values ranging from 6.0 to 8.0. The efficient biosensor was applied to the simultaneous detection of Cu+ and pH in the live brain. The average levels of Cu+ were reported for the first time in the cortex, hippocampus, and striatum in a mouse model of Alzheimer's disease. [ABSTRACT FROM AUTHOR]

Reversible stepwise chain growth in linear CuI assemblies can be achieved by using the dynamic, unsymmetric naphthyridinone-based ligand scaffolds L1 and L2. With the same ligand scaffolds, the length of the linear copper chain can be varied from two to three and four copper atoms, and the nuclearity of the complex is easily controlled by the stepwise addition of a CuI precursor to gradually increase the chain length, or by the reductive removal of Cu atoms to decrease the chain length. This represents a rare example of a stepwise controlled chain growth in extended metal atom chains (EMACs). All complexes are formed with excellent selectivity, and the mutual transformations of the complexes of different nuclearity were found to be fast and reversible. These unusual rearrangements of metal chains of different nuclearities were achieved by a stepwise 'sliding' movement of the naphthyridinone bridging fragment along the metal chain. [ABSTRACT FROM AUTHOR]

Mixtures of uniform sequence-defined oligourethanes are evaluated as 2D molecular barcodes for labeling three different commodity polymers, namely polystyrene, polyvinylchloride and polyethylene terephthalate. Six different oligourethanes are synthesized by solid-phase iterative synthesis and are coded using a binary monomer alphabet. High-resolution mass spectrometry studies indicate that all oligomers are uniform and sequence-defined. However, instead of using them as individual coded chains, oligomers with different chain-length, mass and sequence are mixed into intentionally polydispersed libraries. In particular, a three-component library and a four-component library are created to encode a 2-bytes model binary sequence. These 2D-coded libraries are incorporated in all commodity plastics via a simple solvent casting procedure. Furthermore, in all cases, the oligomer mixtures can be extracted from the host polymer films and deciphered by mass spectrometry, thus opening interesting avenues for anti-counterfeiting and traceability applications. [ABSTRACT FROM AUTHOR]

For postpolymerization modification, a novel kinetic Monte Carlo (kMC) modeling strategy for the description of the reaction event history and the evolution of the microstructure of individual macrospecies with a complex topology is presented. The kMC model allows the kinetic analysis of free radical induced grafting of vinyl monomers onto polyethylene (PE) chains, assuming isothermal conditions and perfect macromixing and accounting for diffusional limitations on the microscale. Not only average characteristics such as the monomer conversion, grafting selectivity and yield, but also the chain length distribution (CLD) of all macromolecular species types, the average 'from/to' grafting and cross-linking density, the number of grafts and cross-links per individual macromolecule, the chain length of every graft, and the CLD of the grafted chains are calculated. Under typical grafting conditions, depropagation and diffusional limitations cannot be ignored. The functionalization occurs mainly on those macrospecies in the PE-CLD with a high mass concentration. © 2017 American Institute of Chemical Engineers AIChE J, 2017 [ABSTRACT FROM AUTHOR]

Here, we report the synthesis, optical properties, and solid-state packing of monodisperse oligomers of diketopyrrolopyrrole (DPP) up to five repeating units. The optical properties of DPP oligomers in solution and the solid state were investigated by a combination of steady-state and transient spectroscopy. Transient absorption spectroscopy and time-correlated single photon counting (TCSPC) measurements show that the fluorescence lifetime decreases with an increase in the oligomer size from monomer to trimer, thereby reaching saturation for pentameric DPP oligomers. The solid-state packing and crystallinity were probed by using advanced techniques, which included grazing incidence small-angle X-ray scattering (GISAXS) and X-ray diffraction (XRD) to elucidate the structure-property trend. Collectively, our chain-length dependent studies establish the fundamental correlation between the structure and property and provide a comprehensive understanding of the solid-state properties in DPP-DPP based conjugated systems. [ABSTRACT FROM AUTHOR]

A series of single-chained N-acyl tyrosine surfactants with varying chain lengths (C10-C18) and degree of unsaturation, as well as an N-acyl Gemini tyrosine surfactant with chain length C12, were synthesized, and the structures were confirmed using spectral analysis. The effect of chain length and level of unsaturation on the physicochemical and antibacterial properties of the N-acyl tyrosine surfactants was evaluated. The C12 derivative displayed the optimum antibacterial activity among the single chain surfactants, and the presence of double bond in the oleoyl derivative enhanced the antibacterial activity over its saturated analogue. The N-acyl Gemini surfactant displayed the highest antibacterial activity among the series and also showed greater micelle forming ability than its single chain analogue. Mixed micellar behavior of the N-acyl Gemini surfactant with conventional cationic (CTAB) and anionic (SDS) surfactants in aqueous solution was studied. The negative value of the interaction parameter β12 observed for the N-acyl Gemini in binary mixture with CTAB surfactant indicated a synergistic interaction within the mixed micellar system. However, the binary mixture with SDS displayed antagonistic behavior. The binary mixture of N-acyl Gemini surfactant with CTAB displayed better antibacterial activity and foaming properties than with SDS mixtures. Optimum antibacterial activity was observed for N-acyl Gemini surfactant with mole ratio 0.4 to 0.6 in the CTAB binary mixture, at which the lowest ocular irritation index was observed. Overall, the study showed that the Gemini surfactant in combination with the conventional surfactant CTAB can be used as potential ingredients in detergent and pharmaceutical formulations. [ABSTRACT FROM AUTHOR]

Amphiphilic random copolyacrylamides bearing hydrophilic poly(ethylene glycol) (PEG) and hydrophobic dodecyl pendants induce precision self-assembly to produce quite small uniform and/or necklace micelles (≈10 nm) in water. The size, structure, and thermoresponsive properties of the micelles are controlled by the primary structure (composition and chain length) of the copolymers. For this, random copolymers with different composition, chain length, and molecular weight distribution are synthesized by iron-catalyzed living or free radical copolymerization of PEG acrylamide and dodecyl acrylamide (DAAm). The copolymers with controlled molecular weight (degree of polymerization: ≈40) intermolecularly self-assemble and/or self-fold to form uniform (multichain or unimer) micelles in water; the size increases with increasing hydrophobic DAAm content (19-57 mol%: Mw = 43 900-191 000). In contrast, random copolymers with relatively small DAAm content (<35 mol%) and broad molecular weight distribution provide both uniform and necklace micelles in water. [ABSTRACT FROM AUTHOR]

Based on theoretical analysis, the effect of polydispersity on particle penetration into polydisperse polymer brushes is investigated. Three different polydispersities representing sharp, moderate, and extremely wide chain length distributions are chosen, since the corresponding explicit expressions of brush density at these polydispersities are available. To simplify the discussion, this study is restricted to spherical particles of small size which ensure that the particle insertion only causes local conformational perturbations. By analyzing the particle distribution, it is found that polydispersity always facilitates particle penetration. This prediction is confirmed by analyzing the surface fluctuations of the brushes. Interestingly, uniform scaling relations are observed for particles penetrating into monodisperse and moderately polydisperse brushes. The uniformity predicted by monodisperse and moderately polydisperse brushes originates from the same asymptotic behavior of their densities approaching the brush edge. This indicates that polydispersity brings significant influence only at high polydispersities. [ABSTRACT FROM AUTHOR]

Copolymer properties and processability depend on copolymer microstructure, i.e., copolymer composition and monomer unit arrangements along the copolymer chains. To predict the ultimate properties of copolymers, one needs complete information on the length and position of sequences of each monomer type in every chain. A versatile kinetic Monte Carlo code is developed and applied for the simulation of typical free radical copolymerizations. The code allows explicit monitoring of every growing chain during the course and at the end of polymerization, can account for comonomer systems of any arbitrary reactivity ratios ( r1 and r2) over the full range of monomer composition. Meanwhile, it eliminates the need for solving arrays of differential equations arising from deterministic modeling approaches. Since the code virtually synthesizes billions of copolymer molecules and keeps in storage information on each and every copolymer chain in the system, it allows for detailed statistical analysis. The simulator visualizes the bivariate sequence length-chain length distribution for typical copolymerization systems and examples with: r1 < 1 and r2 < 1; r1 > 1 and r2 < 1; ( r1 × r2) = 1; and r1 = r2 = 1, and is also applied successfully to an experimental scenario described in the literature. [ABSTRACT FROM AUTHOR]

Despite the evidence supporting a relationship between phenolipid's alkyl chain length and their interaction/affinity with membranes, such a connection has not been directly evaluated. In this study, the membrane interactions of rosmarinic acid, and its corresponding alkyl esters having 4 carbon (RC4), 8 carbon (RC8), 10 carbon (RC10), and 16 carbon (RC16) have been investigated via small angle X-ray scattering (SAXS) approaches in model membrane liposomes. The results of this work show significant differences between the tested phenolipids with respect to their interaction and location within the lipid bilayer. Both membrane affinity and penetration depth follow a nonlinear behavior. They have been shown to increase as a function of increasing alkyl chain length until a threshold is reached for medium alkyl chain, beyond which any lengthening of the chain results in a collapse. RC8 show the highest affinity for the membrane, whereas RC10 constitute a critical chain length from which the penetration depth decreases. The X-ray scattering analyses seem to perfectly correlate with the phenolipids' activities (antioxidant and membranes crossing) previously observed both in biological system and in formulated lipid dispersions. Practical applications: Phenolic compounds are potent antioxidants that may play an important role as well in biological system as in formulated lipid dispersions. However, their activity is often limited by low solubility or bioavailability. Lipophilization of phenolic compounds may increase their solubility in lipophilic matrices, conferring better antioxidant protection for food or nonfood application. In biological system, lipophilization may contribute to easier penetration of antioxidants through lipid bilayer of cell membranes, which can significantly increase their bioavailability. Despite the evidence supporting a relationship between phenolipid's alkyl chain length and their interaction/affinity with membranes, such a relationship has not been directly evaluated. Investigation of membrane interactions between phenolic and its lipophilic derivative, via SAXS approaches in model membrane liposomes, provide new knowledge about this class of compound with the perspective to be used as substances with maintained or improved biological properties for food, cosmetic and pharmaceutical applications. An X-ray diffraction analysis highlighted different membrane affinity and nonlinear penetration depth of a series of phenolipids (rosmarinic acid, and its corresponding alkyl esters having 4 carbon (RC4), 8 carbon (RC8), 10 carbon (RC10), and 16 carbon (RC16)). The results seem to perfectly correlate with the phenolipids' activities (antioxidant and membranes crossing) previously observed both in biological system and in formulated lipid dispersions. [ABSTRACT FROM AUTHOR]

Separation of single-base substitution sequential DNA isomers remains one of the most challenging tasks in DNA separation by capillary electrophoresis. We developed a simple, versatile capillary electrophoresis technique for the separation of single-base sequential isomers of DNA having the same chain length. This technique is based on charge differences resulting from the different protonation (acid dissociation) properties of the four DNA bases. A mixture of 13 single-base sequential isomers of 12-mer single-stranded DNA was separated by using an electrophoretic buffer solution containing 20 mM phosphoric acid (pH 2.0) and 8 M urea. We demonstrated that our method could separate all possible mutation patterns under identical experimental conditions. In addition, application of our method to the separation of the polymerase chain reaction product of a 68-mer gene fragment and its single-base isomers indicates that in combination with the appropriate genomic DNA extraction techniques, the method can detect single-base gene mutations. [ABSTRACT FROM AUTHOR]

The wet and soft nature of hydrogels makes them useful as a mimic for biological tissues, and in uses such as actuators and drug delivery vehicles. For many applications the mechanical performance of the gel is critical, but gels are notoriously weak and prone to fracture. Free radical polymerization is a very powerful technique allowing for fine spatial and temporal control of polymerization, but also allows for the use of a wide range of monomers and mixtures. In this work, it is demonstrated that extremely tough and extensible hydrogels can be readily produced through simple radical polymerization of acrylamide or acrylic acid with a poly(ethylene oxide) macrocross-linker. These gels, with a water content of 85%, are extremely elastic with an extension much more than 15 000% at 9 MPa true stress. They can be compressed over 98% at a stress of 17 MPa. They are notch-insensitive, and the usual trouser tear test does not work because the tear simply does not propagate. This highly extensible nature seems to be related to very long chain lengths between cross-links and efficient incorporation of chains into the network. [ABSTRACT FROM AUTHOR]

Selected aspects of copolymerization processes carried on at constant comonomer concentrations are analyzed theoretically and modeled by Monte Carlo method. It is confirmed that some combinations of initial parameters lead to stationary conditions of copolymer formation for both irreversible and reversible systems which can be regarded as the first-order Markov chain process. However, this study shows that for many copolymerization systems the stationary conditions are attained only at high number-average degree of polymerization DPn, and for some reversible copolymerizations, attaining equilibrium, stationary conditions are not observed at all. The analysis shows that the chain length distribution (CLD) for copolymerization carried out under steady state conditions at constant comonomer concentrations, equal to equilibrium concentrations for infinitely high DPn, is approximately described by the modified Bessel and exponential functions. This type of CLD is analytically proved and confirmed by the Monte Carlo simulations for the analogous homopolymerization process. [ABSTRACT FROM AUTHOR]

The functional characterization of wax biosynthetic enzymes in transgenic plants has opened the possibility of producing tailored wax esters ( WEs) in the seeds of a suitable host crop. In this study, in addition to systematically evaluating a panel of WE biosynthetic activities, we have also modulated the acyl-CoA substrate pool, through the co-expression of acyl- ACP thioesterases, to direct the accumulation of medium-chain fatty acids. Using this combinatorial approach, we determined the additive contribution of both the varied acyl-CoA pool and biosynthetic enzyme substrate specificity to the accumulation of non-native WEs in the seeds of transgenic Camelina plants. A total of fourteen constructs were prepared containing selected FAR and WS genes in combination with an acyl- ACP thioesterase. All enzyme combinations led to the successful production of wax esters, of differing compositions. The impact of acyl-CoA thioesterase expression on wax ester accumulation varied depending on the substrate specificity of the WS. Hence, co-expression of acyl- ACP thioesterases with Marinobacter hydrocarbonoclasticus WS and Marinobacter aquaeolei FAR resulted in the production of WEs with reduced chain lengths, whereas the co-expression of the same acyl- ACP thioesterases in combination with Mus musculus WS and M. aquaeolei FAR had little impact on the overall final wax composition. This was despite substantial remodelling of the acyl-CoA pool, suggesting that these substrates were not efficiently incorporated into WEs. These results indicate that modification of the substrate pool requires careful selection of the WS and FAR activities for the successful high accumulation of these novel wax ester species in Camelina seeds. [ABSTRACT FROM AUTHOR]

Star-shaped bio-based resins were synthesized by direct condensation of lactic acid ( LA) with xylitol followed by end-functionalizing of branches by methacrylic anhydride with three different LA chain lengths (3, 5 and 7). The thermomechanical and structural properties of the resins were characterized by 13C NMR, Fourier transform IR spectroscopy, rheometry, DSC, dynamic mechanical analysis ( DMA), TGA and flexural and tensile tests. An evaluation of the effect of chain length on the synthesized resins showed that the resin with five LAs exhibited the most favorable thermomechanical properties. Also, the resin's glass transition temperature (103 °C) was substantially higher than that of the thermoplast PLA ( ca 55 °C). The resin had low viscosity at its processing temperature (80 °C). The compatibility of the resin with natural fibers was investigated for biocomposite manufacturing. Finally, composites were produced from the n5-resin (80 wt% fiber content) using jute fiber. The thermomechanical and morphological properties of the biocomposites were compared with jute- PLA composites and a hybrid composite made of the impregnated jute fibers with n5 resin and PLA. SEM and DMA showed that the n5-jute composites had better mechanical properties than the other composites produced. Inexpensive monomers, good thermomechanical properties and good processability of the n5 resin make the resin comparable with commercial unsaturated polyester resins. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Starting from common monounsaturated fatty acids, a strategy is revealed that provides ultra-long aliphatic α,ω-difunctional building blocks by a sequence of two scalable catalytic steps that virtually double the chain length of the starting materials. The central double bond of the α,ω-dicarboxylic fatty acid self-metathesis products is shifted selectively to the statistically much-disfavored α,β-position in a catalytic dynamic isomerizing crystallization approach. 'Chain doubling' by a subsequent catalytic olefin metathesis step, which overcomes the low reactivity of this substrates by using waste internal olefins as recyclable co-reagents, yields ultra-long-chain α,ω-difunctional building blocks of a precise chain length, as demonstrated up to a C48 chain. The unique nature of these structures is reflected by unrivaled melting points ( Tm=120 °C) of aliphatic polyesters generated from these telechelic monomers, and by their self-assembly to polyethylene-like single crystals. [ABSTRACT FROM AUTHOR]

The dehydratase domains (DHs) of the iso-migrastatin (iso-MGS) polyketide synthase (PKS) were investigated by systematic inactivation of the DHs in module-6, -9, -10 of MgsF (i.e., DH6, DH9, DH10) and module-11 of MgsG (i.e., DH11) in vivo, followed by structural characterization of the metabolites accumulated by the mutants, and biochemical characterization of DH10 in vitro, using polyketide substrate mimics with varying chain lengths. These studies allowed us to assign the functions for all four DHs, identifying DH10 as the dedicated dehydratase that catalyzes the dehydration of the C17 hydroxy group during iso-MGS biosynthesis. In contrast to canonical DHs that catalyze dehydration of the β-hydroxy groups of the nascent polyketide intermediates, DH10 acts in a long-range manner that is unprecedented for type I PKSs, a novel dehydration mechanism that could be exploited for polyketide structural diversity by combinatorial biosynthesis and synthetic biology. [ABSTRACT FROM AUTHOR]

BACKGROUND 3-monochloro-1, 2-propanediol fatty acid esters (3- MCPDEs) comprise a group of food toxicants formed during food processing. 3- MCPDEs have received increasing attention concerning their potential negative effects on human health. However, reports on the toxicity of 3- MCPD esters are still limited. To determine the effects of fatty acid substitutions on the toxicity of their esters, 1-stearic, 1-oleic, 1-linoleic, 1-linoleic-2-palmitic and 1-palmitic-2-linoleic acid esters of 3- MCPD were synthesized and evaluated with respect to their acute oral toxicities in Swiss mice. RESULTS 3- MCPDEs were obtained through the reaction of 3- MCPD and fatty acid chlorides, and their purities and structures were characterized by ultraperformance liquid chromatography-quadrupole-time of flight-mass spectrometry (UPLC-Q-TOF-MS), infrared, 1H and 13C spectroscopic analyses. Medial lethal doses of 1-stearic, 1-oleic, 1-linoleic, 1-linoleic-2-palmitic and 1-palmitic-2-linoleic acid esters were 2973.8, 2081.4, 2016.3, 5000 and > 5000 mg kg−1 body weight. For the first time, 3- MCPDEs were observed for their toxic effects in the thymus and lung. In addition, major histopathological changes, as well as blood urea nitrogen and creatinine, were examined for mice fed the five 3- MCPDEs. CONCLUSION The results from the present study suggest that the degree of unsaturation, chain length, number of substitution and relative substitution locations of fatty acids might alter the toxicity of 3- MCPDEs. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

For the first time a new analytical procedure to analyze small oligomers produced in a butyl acrylate-methyl methacrylate emulsion copolymerization is applied. With this method, low molecular weight co-oligomers are studied using MALDI-ToF-MS. Both the oligomers in the aqueous phase and the oligomers in the particle phase can be seen. Varying the initiator system, it is observed that the initiation step has an influence on the composition of these oligomers and hence on the absorption on to latex particles. Chain length dependent average compositions in the aqueous phase are observed. The chain length dependent oligomer composition can be described in terms of kinetic effects and preferential/selective adsorption of co-oligomers on the particle surface. The kinetic effects and the extent of adsorption on the particle phase are both dependent on the various end groups. The preferential/selective adsorption of co-oligomers on the particle phase is explained on the basis of solubility and interactions with the surface. The chain length dependent absolute oligomer amount decreases exponentially with chain length as confirmed by Monte Carlo simulations. This information is important to further understand the events of the aqueous phase of an emulsion copolymerization as well as the entry of radicals into the particles. [ABSTRACT FROM AUTHOR]

The importance of the development of kinetic modeling tools to mechanistically understand and design bulk and solution reversible addition fragmentation chain transfer (RAFT) polymerization is highlighted. Both deterministic and stochastic kinetic modeling methods are covered, considering a detailed reaction scheme and accounting for the impact of diffusional limitations on the reaction rates. A novel strategy is introduced to fundamentally calculate the diffusional contributions for the apparent RAFT addition and fragmentation rate coefficients. Next to literature examples, case studies are included to demonstrate that detailed theoretical studies are indispensable to completely map the effect of the polymerization conditions and RAFT agent reactivity on the control over microstructural properties and the overall polymerization time. Guidelines for future kinetic modeling activities are formulated to enhance joined theoretical and experimental research. [ABSTRACT FROM AUTHOR]

The vaporization thermodynamics of symmetric imidazolium based ionic liquids of the general formula [C nC nIm][Br] with the chains length n = 4, 5, 6, and 8 were investigated using a combination of DSC, TGA, and QCM methods with quantum chemical calculations. Comparison of vaporization enthalpies for the symmetric ([C nC nIm][Br]) and asymmetric imidazolium based ILs ([C nmim][Br]) revealed a general trend with the lower vaporization enthalpies of the symmetric species indicating a significant decrease of the Coulombic interactions affecting energetics of vaporization. [ABSTRACT FROM AUTHOR]

SUMMARY Biofuel from fatty acids with chain lengths of 8-15 (C8-C15) have properties similar to those of conventional diesel and jet fuels, thus, can save time and reduce costs for the refurbishment of engines and maintenance of oiling facilities. Most oil-producing algae yield C16-C18 fatty acids; however, the manipulation of algae using genetic engineering is a promising approach to obtain C8-C15 fatty acids. The introduction of a medium-chain-specific thioesterase (TE) is expected to effectively alter algae to produce medium-chain fatty acids (MCFAs). TE is the main determinant of fatty acid chain length as it releases fatty acids from the acyl carrier protein (ACP) in the fatty acid elongation cycle. In a previous study, the introduction of heterologous C8-C12-specific TEs into Chlamydomonas reinhardtii did not increase the yield of MCFAs. This effect was attributed to a low affinity of the heterologous TEs to C. reinhardtii ACP. Therefore, we introduced both the C10-C14-specific TE gene and the ACP gene from the land plant Cuphea lanceolata into C. reinhardtii. We measured free fatty acids (FFAs) and triacylglycerols (TAGs) in the transformants using liquid chromatography-mass spectrometry. The production of C12:0 and C14:0, chain length 12 and 14 without unsaturation, FFAs was not significantly increased in any of the tested strains. However, we found a slight but significant increase in TAG-containing MCFAs in both TE only and TE-ACP transformants. The increased production rate of C14:0-containing TAGs ranged from 1.25- to 1.58-fold, indicating the ability of medium-chain-specific TE to increase MCFAs. These results suggest that the selection of specific TEs is important when modifying eukaryotic algae to produce MCFAs. [ABSTRACT FROM AUTHOR]

ABSTRACT The hydrolysis reaction of O,O-diethyl O- p-nitrophenylphosphate (Paraoxon) with the octanohydroxamate ion (OHA−) was studied in a cationic oil-in-water (O/W) microemulsion system over a pH range 7.5-12.0 at 300 K. The O/W systems are stabilized by using cationic surfactant, cetyltrimethylammonium bromide (CTAB), and n-butanol as cosurfactants. In a microemulsion, the rate enhancement by OHA− is greater toward the cleavage of paraoxon than its spontaneous (2.1 × 107 s−1) hydrolysis. The kobs values for the reaction of paraoxon with OHA− were determined in different microemulsion compositions with varying chain length of alcohols ( n-butanol, n-pentanol, n-octanol, and n-dodecanol) and alkanes ( n-hexane, n-heptane, and n-decane). The effects of water content, pH, and size of the oil pool have been discussed. [ABSTRACT FROM AUTHOR]

The highly constrained β-amino acid ABOC induces different types of helices in β urea and 1:1 α/β amide oligomers. The latter can adopt 11/9- and 18/16-helical folds depending on the chain length in solution. Short peptides alternating proteinogenic α-amino acids and ABOC in a 2:1 α/β repeat pattern adopted an unprecedented and stable 12/14/14-helix. The structure was established through extensive NMR, molecular dynamics, and IR studies. While the 1:1 α-AA/ABOC helices diverged from the canonical α-helix, the helix formed by the 9-mer 2:1 α/β-peptide allowed the projection of the α-amino acid side chains in a spatial arrangement according to the α-helix. Such a finding constitutes an important step toward the conception of functional tools that use the ABOC residue as a potent helix inducer for biological applications. [ABSTRACT FROM AUTHOR]

Twelve symmetrical dimeric materials consisting of a nonamethylene (C9) spacer and either phenyl 4-(4′-alkylphenyl)benzoate, phenyl 4-(4′-alkylcyclohexyl)benzoate or phenyl 4-(4′-alkylbicyclohexyl)carboxylate mesogenic units were prepared and their mesogenic behaviour characterised by POM, DSC and XRD. All of the materials exhibited nematic phases with clearing points in excess of 200 °C. Four compounds were found to exhibit the twist-bend nematic phase, with one material exhibiting a transition from the NTB phase into an anticlinic smectic 'X' phase. Across all three series of compounds the length of terminal chain is seen to dictate, to some degree, the type of mesophase formed: shorter terminal chains favour nematic and NTB mesophases, whereas longer terminal aliphatic chains were found to promote smectic phases. [ABSTRACT FROM AUTHOR]

Long-chain branching plays an important role in the performance of polyolefins (POs). The existence of a very small amount of long-chain branches (LCBs), i.e., <1 per 10 000 carbons, can significantly improve processability of the polyolefin materials, which is highly desired for those intractable polyolefins with narrow molecular weight distribution and high degree of crystallinity. Numerous literatures have been published on the controlled synthesis of long-chain-branched POs. In the previous paper, the major literatures of single catalyst systems have been summarized. This paper provides a comprehensive review for the binary and multiple catalyst systems and a brief summary of some other methods for the controlled synthesis of long-chain-branched POs. The controllability of long-chain-branched structures in the various preparation procedures with single or two reactor systems, and in one or two-step processes, is analyzed and compared in-depth. [ABSTRACT FROM AUTHOR]

Polymer-dispersed liquid crystals (PDLCs) have garnered significant interest and motivated the investigation of the phase behavior of thermally stable smectic liquid crystals (LCs) via thermally induced phase separation (TIPS). In this study, we examined a series of two, biphenyl-based smectic LCs suitable for high temperature polymer blend processing. Phase diagrams for LC/polystyrene (PS) blends at various compositions (0-60 wt%) were constructed. Less than 15 wt% of 8B8 (1,1'-biphenyl-4,4'-diyl dioctanoate) LC in PS led to good polymer miscibility, while phase separation was induced at concentrations higher than 15 wt%. The LC concentration at saturation decreased with increasing aliphatic chain length. We also investigated the chain length (C6-C16) effect on the PS glass transition temperature (Tg) at the LC saturation point. The Tg increased with increasing chain length due to reduced plasticization. We further examined the role of chemical structure (relatively less polar ether vs. more polar ester) on the phase diagram regions and the Tg of the nonpolar PS matrix, respectively. It is anticipated that these LC/PS phase diagrams will benefit elevated temperature processing for TIPS by highlighting the role of LC chemical structure and chain length on blend morphology. [ABSTRACT FROM AUTHOR]

The thermal and chain length sensitivity of the infrared spectra of some solid state anhydrous silver(I) salts (n-octanoate to n-eicosanoate, inclusive) are discussed. At ambient temperature, the tilted alkyl chains, anchored to the metal planes via chelating bidentate coordination to the silver ions, are crystallized in the fully extended all-trans conformation. Interestingly, though all compounds are crystallized in a monoclinic crystal system, their lateral chain packing, van der Waals effects, and hence vibrational features are chain length-dependent. This is a direct result of electrostatic effects of the COO group in addition to vibrational coupling between CH2, CH3, and COO modes, an effect which varies significantly with chain length. Variable temperature infrared measurements indicate significant irreversible changes in the metal-carboxyl coordination sphere, most likely due to bond fission. For long chain adducts (nc>12), thermally induced crystal system switching, monoclinic to triclinic, indicates greater thermal sensitivity of their alkyl chains. During heating, the regions of the hydrocarbon chains, furthest from the COO, become increasingly molten and mobile as the stepwise melt advances towards the solid COO moieties. This solid-liquid melting behaviour is responsible for mesophase formation in metal carboxylate systems. [ABSTRACT FROM AUTHOR]

SUMMARY The electronic structure of fluorinated self-assembled monolayers (F-SAMs) with different chain lengths was investigated by photoelectron and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. From the measurements of the photoelectron spectra in the wide region and in the C 1s core-level region, the chemical compositions and components of the F-SAMs with different chain length were clarified. In the C K-edge NEXAFS spectra of the F-SAMs, the several spectral features were observed and the intensity of the features at 292 eV and 299 eV decreased with increasing incidence angle of the excitation photons. Based on the results of the photoelectron and NEXAFS spectral measurements, the electronic structure of four F-SAMs with different chain length is discussed. [ABSTRACT FROM AUTHOR]