scholarly journals Synthesis of poly(oxy-2,4-oxanediyl-methylene) by photoinduced cationic polymerization and its acid-catalyzed degradation by UV light

1998 ◽  
Vol 1 (1) ◽  
pp. 97-101 ◽  
Author(s):  
Oskar Nuyken ◽  
R. Benedikt Raether ◽  
Christian E. Spindler
Keyword(s):  
Cationic Polymerization ◽  
Uv Light ◽  
Acid Catalyzed

scholarly journals Electro-Optical Properties of a Polymer Dispersed and Stabilized Cholesteric Liquid Crystals System Constructed by a Stepwise UV-Initiated Radical/Cationic Polymerization

Crystals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 282 ◽  
Author(s):  
Chen-Yue Li ◽  
Xiao Wang ◽  
Xiao Liang ◽  
Jian Sun ◽  
Chun-Xin Li ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Cationic Polymerization ◽  
Uv Light ◽  
Polymer Network ◽  
Reaction Rates ◽  
Driving Voltage ◽  
Material System ◽  
Short Period ◽  
Polymer Dispersed ◽  
New Material

Polymer-dispersed liquid crystal (PDLC) and polymer-stabilized liquid crystal (PSLC) are two typical liquid crystal (LC)/polymer composites. PDLCs are usually prepared by dispersing LC droplets in a polymer matrix, while PSLC is a system in which the alignment of LC molecules is stabilized by interactions between the polymer network and the LC molecules. In this study, a new material system is promoted to construct a coexistence system of PDLC and PSLC, namely PD&SChLC. In this new material system, a liquid-crystalline vinyl-ether monomer (LVM) was introduced to a mixture containing cholesteric liquid crystal (ChLC) and isotropic acrylate monomer (IAM). Based on the different reaction rates between LVM and IAM, the PD&SChLC architecture was built using a stepwise UV-initiated polymerization. During the preparation of the PDS&ChLC films, first, the mixture was irradiated with UV light for a short period of time to induce the free radical polymerization of IAMs, forming a phase-separated microstructure, PDLC. Subsequently, an electric filed was applied to the sample for long enough to induce the cationic polymerization of LVMs, forming the homeotropically-aligned polymer fibers within the ChLC domains, which are similar to those in a PSLC. Based on this stepwise UV-initiated radical/cationic polymerization, a PD&SChLC film with the advantages of a relatively low driving voltage, a fast response time, and a large-area processability is successful prepared. The film can be widely used in flexible displays, smart windows, and other optical devices.

scholarly journals Naphthoxy Bounded Ferrocenium Salts as Cationic Photoinitiators for Epoxy Photopolymerization

2009 ◽  
Vol 2009 ◽  
pp. 1-6
Author(s):  
Zh. Q. Li ◽  
M. Li ◽  
G. L. Li ◽  
Y. Chen ◽  
X. N. Wang ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Infrared Spectroscopy ◽  
Cationic Polymerization ◽  
Uv Light ◽  
Good Thermal Stability ◽  
Long Wavelength ◽  
Dsc Studies ◽  
Arene Ligands ◽  
Epoxy Monomer ◽  
Rate Of Polymerization

To improve the absorption and the bulk of arene ligands, two naphthoxy bounded ferrocenium salts as new cationic photoinitiators, (η6-α-naphthoxybenzene) (η5-cyclopentadienyl) iron hexafluorophosphate (NOFC-1) and (η6-β-naphthoxybenzene) (η5-cyclopentadienyl) iron hexafluorophosphate (NOFC-2), were synthesized, characterized, and studied. NOFC-1 and NOFC-2 were prepared by the reaction of nucleophilic substitution (SNAr) with naphthol and chlorobenzene-cyclopentadienyliron salt. Their activity as cationic photoinitiators was studied using real-time infrared spectroscopy. The results obtained showed that NOFC-1 and NOFC-2 are capable of photoinitiating the cationic polymerization of epoxy monomer directly on irradiation with long-wavelength UV light (365 nm). Comparative studies also demonstrated that they exhibited better efficiency than cyclopentadienyl-Fe-cymene hexafluorophosphate (I-261). When NOFC-1 and NOFC-2 were used to efficiently initiate polymerization of epoxide, both rate of polymerization and final conversion increased using benzoyl peroxide (BPO) as sensitizer. DSC studies showed that NOFC-1 and NOFC-2 photoinitiators in epoxides possess good thermal stability in the absence of light.

scholarly journals Acid-catalyzed transformation of cassane diterpenoids from Caesalpinia bonduc to aromatic derivatives

RSC Advances ◽  
2021 ◽  
Vol 11 (36) ◽  
pp. 22070-22078
Author(s):  
Ting Liu ◽  
Zunxi Ning ◽  
Yan Yin ◽  
Shizhou Qi ◽  
Huiyuan Gao
Keyword(s):  
Uv Light ◽  
Acid Catalyzed ◽  
P Transformations

Transformations of cassane diterpenoids from Caesalpinia bonduc into aromatic derivatives, either in CDCl3 or in CHCl3 irradiated with UV light or catalyzed by AlCl3, were described.

scholarly journals Effect of Cationic Photoinitiator on the Polymerization Kinetics of Vinyl Ether Monomers

2020 ◽  
pp. 48-53
Author(s):  
Tran Nhung Hien Phuong ◽  
Pham Thi Kim Hue ◽  
Luu Bach Hiep ◽  
Hoang Thi Kieu Nguyen
Keyword(s):  
Cationic Polymerization ◽  
Uv Light ◽  
Polymerization Rate ◽  
Conversion Degree ◽  
Emission Characteristics ◽  
Vinyl Monomers ◽  
Curing Process ◽  
Free Radical Photopolymerization ◽  
Acrylic Monomers ◽  
Kinetics Of

In this study, the performance of a new triarylsulfonium photoinitiators in the initiation of cationic polymerization of vinyl monomers was investigated by infrared spectroscopy (IR). The photoinitiator exhibit absorption characteristics compatible with the emission characteristics of medium pressure mercury lamps, which are the main sources of UV light in the industry. The experimental results indicate that the photoinitiator is most effective at a concentration of 1%. At the investigated conditions, the maximal conversion degree is 77.8% and the polymerization rate is 0.56 s-1. The curing process is even faster than the corresponding free-radical photopolymerization of acrylic monomers

Tetrazole 5-Acetic Acid Catalyzed Synthesis and Photophysical Study of 2-Aryl-2,3-dihydroquinolin-4(1H)-ones

2019 ◽  
Vol 16 (3) ◽  
pp. 176-184
Author(s):  
Mohabul A. Mondal ◽  
Abdul Ashik Khan ◽  
Kanchan Mitra
Keyword(s):  
Acetic Acid ◽  
Uv Light ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Mechanistic Study ◽  
Fluorescence Emission Spectra ◽  
Initial Activation ◽  
Photophysical Study ◽  
Acid Catalyzed ◽  
Yellowish White

1H-Tetrazole 5-acetic acid (TAA) has been explored as a new organocatalyst for the synthesis of 2-aryl-2,3-dihydroquinolin-4(1H)-ones derivatives from 2’-aminoacetophenone under solventfree conditions. The method described herein is covenient and the catalyst could be reused. Mechanistic study of the reaction revealed that the reaction passing through initial activation of the aldehyde by the catalyst and the C-C bond formed through the intermolecular pathway. The synthesized compounds exhibit yellowish-white fluorescence when exposed to 350 nm UV light. Optical properties such as absorption and fluorescence emission spectra were monitored in methanol. Fluorescence emission properties in different solvents with different polarity indicate solvatochromic characteristics of the probes.

scholarly journals Photooxidation of cyclohexene in the presence of SO<sub>2</sub>: SOA yield and chemical composition

2017 ◽  
Author(s):  
Shijie Liu ◽  
Long Jia ◽  
Yongfu Xu ◽  
Narcisse T. Tsona ◽  
Shuangshuang Ge ◽  
...  
Keyword(s):  
Urban Areas ◽  
Uv Light ◽  
Organic Aerosol ◽  
Heterogeneous Reactions ◽  
Atmospheric Environment ◽  
Oh Radicals ◽  
Competitive Reaction ◽  
Acid Catalyzed ◽  
Complementary Techniques ◽  
So2 Concentration

Abstract. Secondary organic aerosol (SOA) formation from cyclohexene/NOx system with various SO2 concentrations under UV light was studied to understand the effects of cyclic alkenes on the atmospheric environment in polluted urban areas. A clear decrease at first and then increase of the SOA yield was found with increasing SO2 concentrations. The lowest SOA yield was obtained when initial SO2 concentration was in the range of 30–40 ppb, while higher SOA yield compared to that without SO2 could not be obtained until the initial SO2 concentration was higher than 85 ppb. SOA formation was enhanced by the acid-catalyzed heterogeneous reactions, which lead to an increase in the total organic aerosol mass. The competitive reaction of OH radicals with SO2 and VOCs was the reason for the SOA yield decrease even under acidic conditions. The competitive reaction was an important factor for SOA yield and it should not be neglected in photooxidation, especially when acid-catalyzed mechanism could not significantly improve SOA yield. The composition of organic compounds in SOA was measured using several complementary techniques including Fourier transform infrared (FTIR) spectrometer, ion chromatograph (IC) and electrospray ionization high-resolution quadrupole mass spectrometer (ESI-HR-MS). We present the first evidence that organosulfates were produced from the photooxidation of cyclohexene in the presence of SO2.

Electron microscopy of keratinocytes cultured on a collagen substrate used as an allograft for the treatment of chronic wounds

1992 ◽  
Vol 50 (2) ◽  
pp. 1104-1105
Author(s):  
Debby A. Jennings ◽  
Michael J. Morykwas ◽  
Louis C. Argenta
Keyword(s):  
Electron Microscopy ◽  
Cell Suspension ◽  
Single Cell ◽  
Chronic Wounds ◽  
Mechanical Stability ◽  
Uv Light ◽  
Type I ◽  
Single Cell Suspension ◽  
Collagen Substrate ◽  
Dermal Collagen

Grafts of cultured allogenic or autogenic keratlnocytes have proven to be an effective treatment of chronic wounds and burns. This study utilized a collagen substrate for keratinocyte and fibroblast attachment. The substrate provided mechanical stability and augmented graft manipulation onto the wound bed. Graft integrity was confirmed by light and transmission electron microscopy.Bovine Type I dermal collagen sheets (100 μm thick) were crosslinked with 254 nm UV light (13.5 Joules/cm2) to improve mechanical properties and reduce degradation. A single cell suspension of third passage neonatal foreskin fibroblasts were plated onto the collagen. Five days later, a single cell suspension of first passage neonatal foreskin keratinocytes were plated on the opposite side of the collagen. The grafts were cultured for one month.The grafts were fixed in phosphate buffered 4% formaldehyde/1% glutaraldehyde for 24 hours. Graft pieces were then washed in 0.13 M phosphate buffer, post-fixed in 1% osmium tetroxide, dehydrated, and embedded in Polybed 812.

A photoelectron microscope study of surfaces

1989 ◽  
Vol 47 ◽  
pp. 10-11
Author(s):  
W. Engel ◽  
M. Kordesch ◽  
A. M. Bradshaw ◽  
E. Zeitler
Keyword(s):  
Electron Microscopy ◽  
High Pressure ◽  
Field Strength ◽  
Uv Light ◽  
Physical Property ◽  
Photon Flux ◽  
Mercury Lamp ◽  
Object Surface ◽  
The Sixties ◽  
Physical Features

Photoelectron microscopy is as old as electron microscopy itself. Electrons liberated from the object surface by photons are utilized to form an image that is a map of the object's emissivity. This physical property is a function of many parameters, some depending on the physical features of the objects and others on the conditions of the instrument rendering the image.The electron-optical situation is tricky, since the lateral resolution increases with the electric field strength at the object's surface. This, in turn, leads to small distances between the electrodes, restricting the photon flux that should be high for the sake of resolution.The electron-optical development came to fruition in the sixties. Figure 1a shows a typical photoelectron image of a polycrystalline tantalum sample irradiated by the UV light of a high-pressure mercury lamp.

Sign in / Sign up

Export Citation Format

Share Document