Heavily fluorinated electronic polymers

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2011.Vita. Cataloged from PDF version of thesis.Includes bibliographical references.Building blocks, containing majority fluorine content by weight, for PPEs and PPVs have been synthesized. Some of the monomers were shown to give exclusively fluorous-phase soluble polymers, the syntheses of which were achieved by fluorous biphasic polymerization conditions. Perfluoroalkylated PPEs were found to have excellent fluorescence quantum yields and photophysical and chemical stability, and were used to demonstrate their capability in sensing electron-rich aromatic systems via fluorescence quenching. Perfluoroalkylated PPVs were shown to have poor solubility in both fluorous and non-fluorous solvents. Furthermore, the polymer displayed extremely high stability. Utilizing the fluorous solubility of perfluoroalkylated PPE, fluorescent fluorocarbon-in-water emulsions were achieved. When perfluoroalkylated carboxylate was used as the surfactant, emulsions with surfaces that could be modified via amide-bond forming reactions were obtained. When tagged with biotin, these emulsions showed large degrees of aggregation in the presence of streptavidin. The final chapter of this thesis describes an amide-bond forming reaction to attach gold nanoparticles selectively to the termini of single-walled carbon nanotubes utilizing surfactants to protect the sidewalls of nanotubes.by Jeewoo Lim.Ph.D

Modular synthesis of functional polymer nanoparticles from a versatile platform based on poly(pentafluorophenylmethacrylate)

Control of functionalities in polymer nanoparticles (PNPs) is important for their application. Thus, there is an interest for well-defined nanoparticle platforms to which desired functions could readily, and in modular fashion, be imparted. Herein, we report an amine-reactive PNP platform for the modular synthesis of functional PNPs from poly(pentafluorophenylmethacrylate) (poly(PFPMA)) through a simple substitution/nanoprecipitation/photo-crosslinking strategy. Substitution of amine containing coumarin into poly(PFPMA) allows for the achievement of structural stability of nanoprecipitated particles through photo-crosslinking after nanoprecipitation, making it possible to carry out subsequent chemical transformations in organic solvents if needed. We demonstrate that various small molecules and an amine-terminated polymer could be used to modify the crosslinked PNPs to endow them with various functions including fluorescence and responsiveness to temperature changes. The functional PNPs were characterized with variable temperature dynamic light scattering (DLS), UV-vis, and photoluminescence (PL) spectroscopy, and transmission electron microscopy (TEM). (C) 2016 Wiley Periodicals, Inc.N

Inverse Vulcanization Polymers with Enhanced Thermal Properties via Divinylbenzene Homopolymerization-Assisted Cross-Linking

High-refractive-index sulfur-rich polymers with significantly improved thermal properties are prepared using divinylbenzene (DVB) as a comonomer in a modified, low-temperature inverse vulcanization with elemental sulfur. Differential scanning calorimetry and Fourier transform infrared studies reveal that under the modified inverse vulcanization conditions, homopolymerized DVB segments form, leading to high glass-transition temperatures (T-g > 100 degrees C) and thermal stability previously unattainable from the inverse vulcanization of bifunctional olefin comonomers. On the basis of the modified procedures, a three-step molding process of the inverse vulcanization product of DVB, poly(S-r-DVB), involving (1) prepolymer formation, (2) hot-press compression molding of the soft prepolymer, and (3) thermal annealing of the molded product is demonstrated. The molded high-sulfur-content poly(S-r-DVB) exhibits a high refractive index (n > 1.85), along with high midwave infrared transmittance. Combined with a high T-g, these properties render poly(S-r-DVB) with properties highly desirable in applications involving infrared optics.N

Scattering model for tetrapods with cylindrical arms

A scattering model for regular tetrapods, which are the endoskeleton structure of regular tetrahedrons, is presented. Since a tetrapod, unlike spheres and cylinders, is an anisotropic structure formed by four cylinders branching out from the centroid to the vertices of a tetrahedron, additional symmetry elements and random orientation must be accounted for to develop its scattering model. The scattering function of tetrapods was derived from the modification of the scattering model for cylinders and their structural regularity was simplified. Scattering intensity profiles and pair distance distribution functions were obtained by numerical calculation and compared with the experimental data from small angle X-ray measurements of CdSe tetrapod nanocrystals.OAIID:RECH_ACHV_DSTSH_NO:T201723361RECH_ACHV_FG:RR00200001ADJUST_YN:EMP_ID:A004677CITE_RATE:2.199FILENAME:Scattering model for tetrapods with cylindrical arms.pdfDEPT_NM:화학생물공학부EMAIL:[email protected]_YN:YFILEURL:https://srnd.snu.ac.kr/eXrepEIR/fws/file/e0d81a2c-d396-4d6c-bb15-5b2cb566482a/linkN

Regiospecific Synthesis of Au-Nanorod/SWCNT/Au-Nanorod Heterojunctions

The synthesis of precisely defined nanoscale hybrid materials remains a challenge at the frontier of chemistry and material science. In particular, the assembly of diverse high-aspect ratio one-dimensional materials such as gold nanorods and carbon nanotubes into functional systems is of ever increasing interest due to their electronic and sensing applications. To meet these challenges, methods for interfacing gold nanorods with carbon materials such as single-walled carbon nanotubes (SWCNTs) in a regio-controlled manner are needed. Herein, we report a method for the regiospecific synthesis of terminally linked gold nanorod-SWCNTs based on a nanotube surface protection strategy. The key to our approach is a SWCNT surface protection procedure allowing for selective functionalization of the SWCNT termini.National Science Foundation (U.S.). (ECCS-0731100)United States. Army Research Office (W911NF-07-D-0004)National Institutes of Health (U.S.). National Institute of General Medical Sciences (U.S.) Postdoctural Fellowship (1-F32-GM087028-01A1

Controlled Phase Separation in Poly(p-phenyleneethynylene) Thin Films and Its Relationship to Vapor-Sensing Properties

In this paper, we report the synthesis and mesoporous film formation of hydrophobic rodlike poly(pphenyleneethynylene)s (PPEs) and present porosity-dependent quenching studies using 1,3,5-trinitrotoluene (TNT) vapors. Nonsolvent vapor-induced phase separation was used to induce pore formation during film casting, and the concentration of PPEs in the casting solution was controlled carefully to prevent excimer formation. We found that the structures of the sidechains of the PPEs strongly influence the range of relative humidity at which controlled pore generation occurs, which could be rationalized from interfacial energies calculated from contact angle measurements. Porosity of the PPE films resulted in increased efficiency of fluorescence quenching toward TNT vapors, which previously required very thin films (below 5 nm) for sensing applications. The control of the porous structure as well as film thickness constitutes a promising strategy for enhancing the efficiency of chemosensors and in more general applications requiring fine-tuned polymer-gas interactions.N

A one-pot synthesis of polysulfane-bearing block copolymer nanoparticles with tunable size and refractive index

A one-pot synthesis of sulfur-rich polymer nanoparticles through a ring-opening metathesis polymerization is reported. The nanoparticles are formed in situ from diblock copolymers containing a polynorbornene derivative bearing cyclic polysulfanes. The refractive indices of the resulting nanoparticles are readily controlled in the range from 1.54 to nearly 1.65.N

Fine particulate concentrations over East Asia derived from aerosols measured by the advanced Himawari Imager using machine learning

Fine particulate matter with a diameter below 2.5 lim (PM2.5) is deleterious to the cardiovascular and respiratory systems. It is often difficult to assess the effects of PM2.5 on human health over regions with limited ground monitoring sites, especially in East Asia. As an alternative, we estimated near-surface PM2.5 concentrations by analyzing Advanced Himawari Imager (AHI) Yonsei Aerosol Retrieval (YAER) products. This study incorporates daytime data for East Asia covering the Korean Peninsula, China, Japan, Southeast Asia, and southern Mongolia. We collocated AHI YAER product pixels with meteorological, land-cover, and other ancillary data for the period from March 2018 to February 2019. To estimate PM2.5 concentrations over wide areas spanning many countries displaying various relationships between aerosol optical depth and PM2.5, monthly models were developed by considering both the spatial and temporal characteristics of ground-based PM2.5 measurements. Random forest machine learning model estimated ground-level mass concentrations of PM2.5; subsequent 10-fold cross vali-dation (CV) yielded a CV R-2 value of 0.81 and a CV root mean squared error (RMSE) of 12.3 lig m(-3). We investigated the spatial pattern of PM2.5 concentrations over multiple countries and seasonal variation in PM2.5 concentrations. Diurnal variation of a severe PM2.5 event in the Korean Peninsula was investigated as a case study. The model captured the extremely heterogeneous spatial distribution of PM2.5 concentrations peaked around local noon. To measure the capability of the developed model to estimate PM2.5 concentrations in areas with few in-situ data, its predictive performance was evaluated using a dataset independent of the training process with an R-2 of 0.60 and RMSE of 8.18 lig m(-3). This study demonstrates the potential for satellite-based PM2.5 estimation for areas with insufficient measuring stations

Controlled spatial dispersion of CdSe tetrapod nanocrystals with amphiphilic block copolymer particles

We report, for the first time, a nanoscale control of the spatial distribution of semiconducting tetrapod (TP) nanocrystals within block copolymer particles. Polystyrene (PS) block copolymer (BCP)/CdSe TP nanocrystal hybrid particles were prepared by the nanoprecipitation of TP/BCP mixtures into methanol. The BCPs consisted of short, polar terminal block bearing methyl disulfide anchoring moiety which serves both to bind to CdSe TP surfaces as well as to drive self-assembly during nanoprecipitation into polar solvent systems. The resulting BCP/TP hybrid particles showed various spatial distribution and the number density of TPs with respect to individual polymer particles depending on the degree of polymerization of the block copolymer as well as the nature of the solvent in which nanoprecipitation was done. (C) 2016 Elsevier Ltd. All rights reserved.N