scholarly journals A Review of the Surface Modification of Cellulose and Nanocellulose Using Aliphatic and Aromatic Mono- and Di-Isocyanates

Molecules ◽  
2019 ◽  
Vol 24 (15) ◽  
pp. 2782 ◽  
Author(s):  
Hatem Abushammala ◽  
Jia Mao
Keyword(s):  
Surface Modification ◽  
Functional Groups ◽  
Phenyl Isocyanate ◽  
Hexamethylene Diisocyanate ◽  
Toluene Diisocyanate ◽  
Diphenylmethane Diisocyanate ◽  
Chemical Modifications ◽  
Advantages And Disadvantages ◽  
Wide Range ◽  
Simple Molecules

Nanocellulose has been subjected to a wide range of chemical modifications towards increasing its potential in certain fields of interest. These modifications either modulated the chemistry of the nanocellulose itself or introduced certain functional groups onto its surface, which varied from simple molecules to polymers. Among many, aliphatic and aromatic mono- and di-isocyanates are a group of chemicals that have been used for a century to modify cellulose. Despite only being used recently with nanocellulose, they have shown great potential as surface modifiers and chemical linkers to graft certain functional chemicals and polymers onto the nanocellulose surface. This review discusses the modification of cellulose and nanocellulose using isocyanates including phenyl isocyanate (PI), octadecyl isocyanate (OI), toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HMDI), and their derivatives and polymers. It also presents the most commonly used nanocellulose modification strategies including their advantages and disadvantages. It finally discusses the challenges of using isocyanates, in general, for nanocellulose modification.

Long-term Follow-up of Hexamethylene Diisocyanate-, Diphenylmethane Diisocyanate-, and Toluene Diisocyanate-induced Asthma

2000 ◽  
Vol 162 (2) ◽  
pp. 516-522 ◽  
Author(s):  
PÄIVI L. PIIRILÄ ◽  
HENRIK NORDMAN ◽  
HELENA M. KESKINEN ◽  
RITVA LUUKKONEN ◽  
SUVI-PÄIVIKKI SALO ◽  
...  
Keyword(s):  
Hexamethylene Diisocyanate ◽  
Toluene Diisocyanate ◽  
Diphenylmethane Diisocyanate ◽  
Long Term Follow Up

The Management of Post-Tonsillectomy Morbidity in Patients With Sleep Apnoea

2019 ◽  
Vol 70 (10) ◽  
pp. 3738-3740
Keyword(s):  
Day Surgery ◽  
Sleep Apnoea ◽  
Integrative Approach ◽  
Multicenter Studies ◽  
Therapeutic Modalities ◽  
Advantages And Disadvantages ◽  
Obstructive Sleep ◽  
Wide Range ◽  
The Impact ◽  
Surgery Center

The Tonsillectomy in children or adults is an intervention commonly encountered in the ENT (Ear Nose and Throat) and Head and Neck surgeon practice. The current tendency is to perform this type of surgery in major ambulatory surgery centers. Two objectives are thus pursued: first of all, the increase of the patient quality of life through the reintegration into the family as quickly as possible and secondly, the expenses associated with continuous hospitalization are reduced. Any tertiary (multidisciplinary) sleep center must ensure the complete diagnosis and treatment (including surgery) of sleep respiratory disorders. Under these conditions the selection of patients and especially the implementation of the specific protocols in order to control the postoperative complications it becomes essential. The present paper describes our experience of tonsillectomy as treatment for selected patients with chronic rhonchopathy (snoring) and mild to moderate obstructive sleep apnoea. It was presented the impact of antibiotics protocols in reducing the main morbid outcomes following tonsillectomy, in our day surgery center. The obtained results can also be a prerequisite for the integrative approach of the patients with sleep apnoea who were recommended surgical treatment. Considering the wide range of therapeutic modalities used in sleep apnoea, each with its specific advantages and disadvantages, more extensive and multicenter studies are needed. Keywords: post-tonsillectomy morbidity, day surgery center, sleep disorders

scholarly journals Advancements in Assessments of Bio-Tissue Engineering and Viable Cell Delivery Matrices Using Bile Acid-Based Pharmacological Biotechnologies

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1861
Author(s):  
Armin Mooranian ◽  
Melissa Jones ◽  
Corina Mihaela Ionescu ◽  
Daniel Walker ◽  
Susbin Raj Wagle ◽  
...  
Keyword(s):  
Tissue Engineering ◽  
Viable Cell ◽  
Cell Delivery ◽  
Artificial Organ ◽  
Bioartificial Pancreas ◽  
Advantages And Disadvantages ◽  
Wide Range ◽  
Bioartificial Organs ◽  
Significant Interest ◽  
Modern Technologies

The utilisation of bioartificial organs is of significant interest to many due to their versatility in treating a wide range of disorders. Microencapsulation has a potentially significant role in such organs. In order to utilise microcapsules, accurate characterisation and analysis is required to assess their properties and suitability. Bioartificial organs or transplantable microdevices must also account for immunogenic considerations, which will be discussed in detail. One of the most characterized cases is the investigation into a bioartificial pancreas, including using microencapsulation of islets or other cells, and will be the focus subject of this review. Overall, this review will discuss the traditional and modern technologies which are necessary for the characterisation of properties for transplantable microdevices or organs, summarizing analysis of the microcapsule itself, cells and finally a working organ. Furthermore, immunogenic considerations of such organs are another important aspect which is addressed within this review. The various techniques, methodologies, advantages, and disadvantages will all be discussed. Hence, the purpose of this review is providing an updated examination of all processes for the analysis of a working, biocompatible artificial organ.

Preparation of Functionalized Diorganomagnesium Reagents in Toluene via Bromine or Iodine/Magnesium-Exchange Reactions

Synthesis ◽  
2021 ◽  
Author(s):  
Alexandre Desaintjean ◽  
Fanny Danton ◽  
Paul Knochel
Keyword(s):  
Exchange Reaction ◽  
Nitro Group ◽  
General Formula ◽  
Functional Groups ◽  
Exchange Reactions ◽  
Acyl Chlorides ◽  
Aryl Iodides ◽  
Highly Sensitive ◽  
Wide Range ◽  
Magnesium Exchange

A wide range of polyfunctionalized di(hetero)aryl- and dialkenyl-magnesium reagents were prepared in toluene within 10 to 120 min between −78 °C and 25 °C via an I/Mg- or Br/Mg-exchange reaction using reagents of the general formula R2Mg (R = sBu, Mes). Highly sensitive functional groups, such as a triazene or a nitro group, were tolerated in these exchange reactions, enabling the synthesis of various functionalized (hetero)arenes and alkenes derivatives after quenching with several electrophiles including allyl bromides, acyl chlorides, aldehydes, ketones, and aryl iodides.

scholarly journals Surface modification of cellulose nanocrystals

Nanoscale ◽  
2014 ◽  
Vol 6 (14) ◽  
pp. 7764-7779 ◽  
Author(s):  
Samuel Eyley ◽  
Wim Thielemans
Keyword(s):  
Surface Modification ◽  
Cellulose Nanocrystals ◽  
Nanocrystalline Cellulose ◽  
Chemical Modifications

This review takes an in-depth look at the chemical modifications that have been carried out on nanocrystalline cellulose.

scholarly journals Ureido Functionalization through Amine-Urea Transamidation under Mild Reaction Conditions

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1583
Author(s):  
Natalia Guerrero-Alburquerque ◽  
Shanyu Zhao ◽  
Daniel Rentsch ◽  
Matthias M. Koebel ◽  
Marco Lattuada ◽  
...  
Keyword(s):  
Aqueous Media ◽  
Reaction Times ◽  
Reaction Rates ◽  
Secondary Amines ◽  
Isocyanic Acid ◽  
Advantages And Disadvantages ◽  
Major Disadvantage ◽  
Wide Range ◽  
Potential Alternative ◽  
Full Conversion

Ureido-functionalized compounds play an indispensable role in important biochemical processes, as well as chemical synthesis and production. Isocyanates, and KOCN in particular, are the preferred reagents for the ureido functionalization of amine-bearing compounds. In this study, we evaluate the potential of urea as a reagent to graft ureido groups onto amines at relatively low temperatures (<100 °C) in aqueous media. Urea is an inexpensive, non-toxic and biocompatible potential alternative to KOCN for ureido functionalization. From as early as 1864, urea was the go-to reagent for polyurea polycondensation, before falling into disuse after the advent of isocyanate chemistry. We systematically re-investigate the advantages and disadvantages of urea for amine transamidation. High ureido-functionalization conversion was obtained for a wide range of substrates, including primary and secondary amines and amino acids. Reaction times are nearly independent of substrate and pH, but excess urea is required for practically feasible reaction rates. Near full conversion of amines into ureido can be achieved within 10 h at 90 °C and within 24 h at 80 °C, and much slower reaction rates were determined at lower temperatures. The importance of the urea/amine ratio and the temperature dependence of the reaction rates indicate that urea decomposition into an isocyanic acid or a carbamate intermediate is the rate-limiting step. The presence of water leads to a modest increase in reaction rates, but the full conversion of amino groups into ureido groups is also possible in the absence of water in neat alcohol, consistent with a reaction mechanism mediated by an isocyanic acid intermediate (where the water assists in the proton transfer). Hence, the reaction with urea avoids the use of toxic isocyanate reagents by in situ generation of the reactive isocyanate intermediate, but the requirement to separate the excess urea from the reaction product remains a major disadvantage.

Ether Synthesis through Reductive Cross-Coupling of Ketones with Alcohols Using Me2SiHCl as both Reductant and Lewis Acid

Synlett ◽  
2017 ◽  
Vol 28 (18) ◽  
pp. 2425-2428 ◽  
Author(s):  
Bill Morandi ◽  
Yong Lee
Keyword(s):  
Functional Groups ◽  
Lewis Acid ◽  
Carbonyl Compounds ◽  
Cross Coupling ◽  
Wide Range ◽  
Direct Cross ◽  
Sterically Hindered ◽  
Polar Functional Groups ◽  
Ether Synthesis ◽  
Dialkyl Ethers

We report that a Lewis acidic silane, Me2SiHCl, can mediate the direct cross-coupling of a wide range of carbonyl compounds with alcohols to form dialkyl ethers. The reaction is operationally simple, tolerates a range of polar functional groups, can be utilized to make sterically hindered ethers, and is extendable to sulfur and nitrogen nucleo­philes.

Simulation of Local Surface Modification in STM by ab initio Quantum Chemistry

1998 ◽  
Vol 05 (02) ◽  
pp. 493-499 ◽  
Author(s):  
V. S. Gurin
Keyword(s):  
Surface Modification ◽  
Ab Initio ◽  
Physical Nature ◽  
Atomic Scale ◽  
Level Shift ◽  
Electrical Field ◽  
High Electrical Field ◽  
Wide Range ◽  
Energy Level Shift ◽  
Ab Initio Approach

Surface modification by means of STM has became a well-known method for the artificial formation of nanometer and atomic scale structures. The physical nature of surface modification can consist in a wide range of phenomena (from mechanical indentation up to specific tip-induced chemistry). The high electrical field at the STM tip is considered to be the main feature of STM modification experiments. The field strength is comparable with intramolecular ones and can influence the chemical bonding in surface structures. The model of STM-stimulated modification is considered using the quantum-chemical ab initio approach for a surface cluster in the high electrical field. The destabilization effect, energy level shift, and bond polarization under the STM tip field occur and can show the atomistic nature of surface transformations in STM.

scholarly journals Bis-NHC–Ag/Pd(OAc)2 Catalytic System Catalyzed Transfer Hydrogenation Reaction

Catalysts ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 8
Author(s):  
Hui-Ju Chen ◽  
Chien-Cheng Chiu ◽  
Tsui Wang ◽  
Dong-Sheng Lee ◽  
Ta-Jung Lu
Keyword(s):  
Functional Groups ◽  
Catalytic System ◽  
High Efficiency ◽  
Aqueous Media ◽  
Hydrogenation Reaction ◽  
Transfer Hydrogenation ◽  
Terminal Alkynes ◽  
Wide Range ◽  
Transfer Hydrogenation Reaction

The bis-NHC–Ag/Pd(OAc)2 catalytic system (NHC = N-heterocyclic carbene), a combination of bis-NHC–Ag complex and Pd(OAc)2, was found to be a smart catalyst in the Pd-catalyzed transfer hydrogenation of various functionalized arenes and internal/terminal alkynes. The catalytic system demonstrated high efficiency for the reduction of a wide range of various functional groups such as carbonyls, alkynes, olefins, and nitro groups in good to excellent yields and high chemoselectivity for the reduction of functional groups. In addition, the protocol was successfully exploited to stereoselectivity for the transformation of alkynes to alkenes in aqueous media under air. This methodology successfully provided an alternative useful protocol for reducing various functional groups and a simple operational protocol for transfer hydrogenation.

Application of neural networks in membrane separation

2020 ◽  
Vol 36 (2) ◽  
pp. 265-310 ◽  
Author(s):  
Morteza Asghari ◽  
Amir Dashti ◽  
Mashallah Rezakazemi ◽  
Ebrahim Jokar ◽  
Hadi Halakoei
Keyword(s):  
Neural Networks ◽  
Chemical Engineering ◽  
Membrane Separation ◽  
Mechanistic Model ◽  
Computing Time ◽  
Permeate Flux ◽  
Practical Applications ◽  
Advantages And Disadvantages ◽  
Wide Range ◽  
Physical And Chemical

AbstractArtificial neural networks (ANNs) as a powerful technique for solving complicated problems in membrane separation processes have been employed in a wide range of chemical engineering applications. ANNs can be used in the modeling of different processes more easily than other modeling methods. Besides that, the computing time in the design of a membrane separation plant is shorter compared to many mass transfer models. The membrane separation field requires an alternative model that can work alone or in parallel with theoretical or numerical types, which can be quicker and, many a time, much more reliable. They are helpful in cases when scientists do not thoroughly know the physical and chemical rules that govern systems. In ANN modeling, there is no requirement for a deep knowledge of the processes and mathematical equations that govern them. Neural networks are commonly used for the estimation of membrane performance characteristics such as the permeate flux and rejection over the entire range of the process variables, such as pressure, solute concentration, temperature, superficial flow velocity, etc. This review investigates the important aspects of ANNs such as methods of development and training, and modeling strategies in correlation with different types of applications [microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), electrodialysis (ED), etc.]. It also deals with particular types of ANNs that have been confirmed to be effective in practical applications and points out the advantages and disadvantages of using them. The combination of ANN with accurate model predictions and a mechanistic model with less accurate predictions that render physical and chemical laws can provide a thorough understanding of a process.

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