The Experts below are selected from a list of 11046 Experts worldwide ranked by ideXlab platform

Trevor Douglas - One of the best experts on this subject based on the ideXlab platform.

  • synthesis of a cross linked Branched Polymer network in the interior of a protein cage
    Journal of the American Chemical Society, 2009
    Co-Authors: Joynal Abedin, Lars O Liepold, Peter A Suci, Mark J Young, Trevor Douglas
    Abstract:

    A goal of biomimetic chemistry is to use the hierarchical architecture inherent in biological systems to guide the synthesis of functional three-dimensional structures. Viruses and other highly symmetrical protein cage architectures provide defined scaffolds to initiate hierarchical structure assembly. Here we demonstrate that a cross-linked Branched Polymer can be initiated and synthesized within the interior cavity of a protein cage architecture. Creating this Polymer network allows for the spatial control of pendant reactive sites and dramatically increases the stability of the cage architecture. This material was generated by the sequential coupling of multifunctional monomers using click chemistry to create a Branched cross-linked Polymer network. Analysis of Polymer growth by mass spectrometry demonstrated that the Polymer was initiated at the interior surface of the cage at genetically introduced cysteine reactive sites. The Polymer grew as expected to generation 2.5 where it was limited by the siz...

  • synthesis of a cross linked Branched Polymer network in the interior of a protein cage
    Journal of the American Chemical Society, 2009
    Co-Authors: Joynal Abedin, Lars O Liepold, Peter A Suci, Mark J Young, Trevor Douglas
    Abstract:

    A goal of biomimetic chemistry is to use the hierarchical architecture inherent in biological systems to guide the synthesis of functional three-dimensional structures. Viruses and other highly symmetrical protein cage architectures provide defined scaffolds to initiate hierarchical structure assembly. Here we demonstrate that a cross-linked Branched Polymer can be initiated and synthesized within the interior cavity of a protein cage architecture. Creating this Polymer network allows for the spatial control of pendant reactive sites and dramatically increases the stability of the cage architecture. This material was generated by the sequential coupling of multifunctional monomers using click chemistry to create a Branched cross-linked Polymer network. Analysis of Polymer growth by mass spectrometry demonstrated that the Polymer was initiated at the interior surface of the cage at genetically introduced cysteine reactive sites. The Polymer grew as expected to generation 2.5 where it was limited by the size constraints of the cavity. The Polymer network was fully cross-linked across protein subunits that make up the cage and extended the thermal stability for the cage to at least 120 degrees C. The introduced reactive centers were shown to be active and their number density increased with increasing generation. This synthetic approach provides a new avenue for creating defined Polymer networks, spatially constrained by a biological template.

Joynal Abedin - One of the best experts on this subject based on the ideXlab platform.

  • synthesis of a cross linked Branched Polymer network in the interior of a protein cage
    Journal of the American Chemical Society, 2009
    Co-Authors: Joynal Abedin, Lars O Liepold, Peter A Suci, Mark J Young, Trevor Douglas
    Abstract:

    A goal of biomimetic chemistry is to use the hierarchical architecture inherent in biological systems to guide the synthesis of functional three-dimensional structures. Viruses and other highly symmetrical protein cage architectures provide defined scaffolds to initiate hierarchical structure assembly. Here we demonstrate that a cross-linked Branched Polymer can be initiated and synthesized within the interior cavity of a protein cage architecture. Creating this Polymer network allows for the spatial control of pendant reactive sites and dramatically increases the stability of the cage architecture. This material was generated by the sequential coupling of multifunctional monomers using click chemistry to create a Branched cross-linked Polymer network. Analysis of Polymer growth by mass spectrometry demonstrated that the Polymer was initiated at the interior surface of the cage at genetically introduced cysteine reactive sites. The Polymer grew as expected to generation 2.5 where it was limited by the siz...

  • synthesis of a cross linked Branched Polymer network in the interior of a protein cage
    Journal of the American Chemical Society, 2009
    Co-Authors: Joynal Abedin, Lars O Liepold, Peter A Suci, Mark J Young, Trevor Douglas
    Abstract:

    A goal of biomimetic chemistry is to use the hierarchical architecture inherent in biological systems to guide the synthesis of functional three-dimensional structures. Viruses and other highly symmetrical protein cage architectures provide defined scaffolds to initiate hierarchical structure assembly. Here we demonstrate that a cross-linked Branched Polymer can be initiated and synthesized within the interior cavity of a protein cage architecture. Creating this Polymer network allows for the spatial control of pendant reactive sites and dramatically increases the stability of the cage architecture. This material was generated by the sequential coupling of multifunctional monomers using click chemistry to create a Branched cross-linked Polymer network. Analysis of Polymer growth by mass spectrometry demonstrated that the Polymer was initiated at the interior surface of the cage at genetically introduced cysteine reactive sites. The Polymer grew as expected to generation 2.5 where it was limited by the size constraints of the cavity. The Polymer network was fully cross-linked across protein subunits that make up the cage and extended the thermal stability for the cage to at least 120 degrees C. The introduced reactive centers were shown to be active and their number density increased with increasing generation. This synthetic approach provides a new avenue for creating defined Polymer networks, spatially constrained by a biological template.

Zhenxing Cheng - One of the best experts on this subject based on the ideXlab platform.

  • hyper branch sensing Polymer batch self assembled on resonant micro cantilevers with a coupling reaction route
    Sensors and Actuators B-chemical, 2015
    Co-Authors: Pengcheng Xu, Haitao Yu, Xinxin Li, Zhenxing Cheng
    Abstract:

    Abstract In order to develop a volume fabrication route for chemical sensors, hydrogen-bond acidic hyper-Branched Polymer is synthesized and directly self-assembled in-batch onto MEMS resonant micro-cantilevers as sensing layer. The batch self-assembly is via a facile coupling reaction between the SH group in the self-assembled monolayer (SAM) and one OH group in the hyper-Branched Polymer. During the self-assembly process of the hyper-Branched Polymer, the polyurethane-industry used isophorone diisocyanate (IPDI) is employed as the key coupling reagent, since the two N C O coupling groups in IPDI feature different reactivity. The N C O group with higher reactivity is firstly reacted with the SH group pre-grown at the cantilever surface. Then, another N C O group with lower reactivity reacts with one OH group in the hyper-Branched Polymer. In this way the hydrogen-bond acidic hyper-branch Polymer can be batch grafted onto a run of micro-cantilevers for uniform sensing to targeted gas. Through this route, the resonant cantilever gas sensors can be batch produced for uniform detection of trace organophosphates (OPs). Based on the specific interaction between the OH sensing group and the P O group in OP, the targeted molecules can be captured by the hyper-Branched sensing Polymer, and the mass addition induced frequency shift of the resonant cantilever is output as sensing signal. Sensing experiment is implemented for the sensors taken from one fabrication batch, resulting in satisfactory consistency in sensing performance. Taking 5 sensors as example, the deviation of the sensing response to 2 ppm dimethyl methylphosphonate (DMMP) is less than 1%. Besides, the sensor shows good repeatability/selectivity and good linear response to various concentrations (300 ppb to 1.5 ppm) of DMMP.

  • Hyper-Branched sensing Polymer directly constructed on a resonant micro-cantilever for the detection of trace chemical vapor
    Journal of Materials Chemistry, 2012
    Co-Authors: Yongjing Liu, Guomin Zuo, Zhenxing Cheng, Dajeong Lee
    Abstract:

    A hyper-Branched Polymer is layer-by-layer self-assembled on a resonant micro-cantilever and, then, functionalized with sensing-terminals for the specific detection of the trace chemical vapor of dimethyl methylphosphonate (DMMP, a typical simulant for nerve agents). The hyper-Branched Polymer is directly constructed on the SiO2 surface of the cantilever via an A2 + B4 layer-by-layer route, where A2 and B4 are complementary interacting groups which undergo coupled linking. After modification with 4-(2-(4-(allyloxy)phenyl)-1,1,1,3,3,3-hexafluoropropan-2-yl)phenol (APHFPP) groups specific to DMMP, the high specific-surface-area hyper-Branched Polymer provides very dense sensing sites to adsorb a great number of DMMP molecules for micro-gravimetric detection. Moreover, the sensing Polymer possesses a “more branches but fewer roots” configuration on the cantilever surface to depress the cross-talk effect caused by adsorption induced cantilever spring-stiffening. Experimental results indicate that, self-assembled with the hyper-Branched sensing Polymer, the resonant cantilevers exhibit rapid and reproducible detection of trace DMMP (with the detection limit lower than 7.2 ppb) and effectively depressed parasitic frequency-shift from the cantilever spring stiffening effect. In addition, the sensor features satisfactory selectivity in the presence of water and organic solvents. When an alternative sensing-group of 2-allylhexafluoroisopropanol (AHFIP) is modified on the hyper-Branched architecture, the cantilever becomes specifically sensitive to trace explosive vapor. Therefore, the developed technique for the functionalization of hyper-Branched Polymer directly grown on a cantilever provides a widely usable micro/nano sensing-platform for the detection of trace chemical vapors.

Teresa Headgordon - One of the best experts on this subject based on the ideXlab platform.

  • water is not a dynamic polydisperse Branched Polymer
    Proceedings of the National Academy of Sciences of the United States of America, 2019
    Co-Authors: Teresa Headgordon, Francesco Paesani
    Abstract:

    In PNAS, Naserifar and Goddard (1) report that their RexPoN water model under ambient conditions comprises a “dynamic polydisperse Branched Polymer,” which they speculate explains the existence of the liquid–liquid critical point (LLCP) in the supercooled region. The observable they rely on to support this is the oxygen–oxygen radial distribution function, gOO, from a dated neutron scattering experiment (1). Although it is well known that neutron scattering is almost exclusively sensitive to hydrogen correlations, and gOO is more reliably obtained from X-ray scattering (2), they make the unsupported statement that “the most reliable gOO curve is neutron where there is no inference from electrons” (1). However, two X-ray gOO curves in figure 1B of … [↵][1]1To whom correspondence may be addressed. Email: thg{at}berkeley.edu. [1]: #xref-corresp-1-1

  • water is not a dynamic polydisperse Branched Polymer
    arXiv: Chemical Physics, 2019
    Co-Authors: Teresa Headgordon, Francesco Paesani
    Abstract:

    The contributed paper by Naserifar and Goddard reports that their RexPoN water model under ambient conditions simulates liquid water as a dynamic polydisperse Branched Polymer, which they speculate explains the existence of the liquid-liquid critical point (LLCP) in the supercooled region. Our work addresses several serious factual errors and needless speculation in their paper about their interpretation of their model and its implication for the LLCP in supercooled water.

Ronald G. Larson - One of the best experts on this subject based on the ideXlab platform.

  • model Branched Polymers synthesis and characterization of asymmetric h shaped polybutadienes
    ACS Macro Letters, 2012
    Co-Authors: Shahinur M Rahman, Ronald G. Larson, Xue Chen, Taihyun Chang, Jimmy W Mays
    Abstract:

    A new type of model Branched Polymer, asymmetric H-shaped polybutadienes, consisting of central crossbars having various combinations of short and long arms attached to the ends of the crossbars, was synthesized using living anionic Polymerization and chlorosilane linking chemistry. The linking agent 4-(dichloromethylsilyl)diphenylethylene provides selective reactivity to attach short or long arms on one side or both sides as desired. The samples were characterized thoroughly by size exclusion chromatography with light scattering detection (SEC-LS) and found to exhibit controlled molecular weights, as well as narrow polydispersity indices (PDIs of 1.01–1.06). Temperature gradient interaction chromatography, a method with far superior resolution as compared to SEC, also shows that these materials are well-defined, with minimal and identifiable impurities.

  • Comparing tube models for predicting the linear rheology of Branched Polymer melts
    Journal of Rheology, 2010
    Co-Authors: Zuowei Wang, Xue Chen, Ronald G. Larson
    Abstract:

    The hierarchical and “bob” (or branch-on-branch) models are tube-based computational models recently developed for predicting the linear rheology of general mixtures of polydisperse Branched Polymers. These two models are based on a similar tube-theory framework but differ in their numerical implementation and details of relaxation mechanisms. We present a detailed overview of the similarities and differences of these models and examine the effects of these differences on the predictions of the linear viscoelastic properties of a set of representative Branched Polymer samples in order to give a general picture of the performance of these models. Our analysis confirms that the hierarchical and bob models quantitatively predict the linear rheology of a wide range of Branched Polymer melts but also indicate that there is still no unique solution to cover all types of Branched Polymers without case-by-case adjustment of parameters such as the dilution exponent α and the factor p2 which defines the hopping dis...

  • Combinatorial Rheology of Branched Polymer Melts
    Macromolecules, 2001
    Co-Authors: Ronald G. Larson
    Abstract:

    An algorithm is presented for predicting the linear viscoelasticity of polydisperse Polymers containing long side branches with arbitrary distributions of branch length and branch location along a backbone. The algorithm gives semiquantitative predictions of literature data for a wide range of polybutadiene melts, including monodisperse linear, star, mixed linear and star, pom-pom, and comb Polymers. Huge differences (several orders of magnitude) are predicted in zero-shear viscosities for samples that have the same weight-average molecular weight (200 000) and the same branching fraction but have different branching structures. It is shown that information on branching structure can be inferred by combinatorially measuring rheological properties on series of blends of the Branched Polymer with a linear, or well-defined Branched, Polymer.