Analysis of the linear methods of determining copolymerization reactivity ratios, 9. Penultimate systems with <i>r</i><sub>2</sub> = 0

Kelen, Tibor; Tüdős, F.; Braun, Dietrich; Czerwiński, Wojciech

doi:10.1002/macp.1990.021910811

Cited by 145 publications

(169 citation statements)

References 14 publications

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“…Outro método linear, embora avaliado somente por relações numéricas, é conhecido como o método YBR [82] . Téc-nicas de estimação de parâmetros baseadas no método dos mínimos quadrados são bastante utilizadas para o cálculo das razões de reatividade.…”

Section: Modelo Terminalunclassified

Uma revisão sobre os processos de polimerização em suspensão

2007

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Resumo: Inúmeros processos podem ser utilizados para produção de materiais poliméricos. Cada processo apresenta características peculiares, que permitem produzir resinas com as mais variadas propriedades, visando a diferentes aplicações do material polimérico final. Os processos de polimerização em suspensão são bastante empregados para produção de resinas poliméricas por apresentarem muitas vantagens, como a facilidade de separação, fácil remoção de calor e controle de temperatura e, principalmente, pelos baixos níveis de impureza e de aditivação no produto final. Por isso, processos de polimerização em suspensão são apropriados para obtenção de produtos para aplicações biotecnológicas e médicas, dentre outras. O objetivo principal deste trabalho é apresentar uma discussão dos aspectos fundamentais inerentes aos processos de polimerização em suspensão, visando a uma compreensão do efeito das principais variáveis de processo sobre o desempenho de polimerizações em suspensão. Mostra-se também que a espectroscopia do infravermelho próximo (NIRS) pode ser muito útil para permitir o monitoramento e o controle em tempo real de processos de polimerização em suspensão, para a obtenção de materiais poliméricos com características especiais. Palavras-chave: Polimerização, suspensão, espectroscopia, infravermelho próximo. A Review on Suspension Polymerization ProcessesAbstract: Several processes can be employed for manufacturing polymer materials. Each process presents some intrinsic features that lead to production of resins with peculiar properties, which define the end-use application of the final polymeric material. Suspension polymerization processes are extensively used because of their many advantages, such as the easy separation of the polymer particles, easy removal of the heat of reaction, easy temperature control and low levels of impurities and additives in the final polymer material. For this reason, suspension polymerization processes are suitable to produce polymer resins for biotechnological and medical applications. The main objective of this work is to discuss the fundamental aspects of suspension polymerization processes, focusing upon the effects of the main process variables on the performance of suspension polymerizations. Additionally, it is shown that near infrared spectroscopy (NIRS) can be useful for monitoring and real time control of suspension processes, allowing for production of polymer beads with controlled morphology.

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Section: Modelo Terminalunclassified

Uma revisão sobre os processos de polimerização em suspensão

2007

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“…In order to calculate the reactivity ratios r 1 and r 2 of the butyl methacrylatemethacrylcyclohexyl POSS pair, a series of polymerization runs at low yield (≤8 wt %) were carried out, reducing the reaction time from 24h to 20 minutes. Results are collected in Table 3 After NMR analysis a calculation of molar fractions were done, and reactivity ratios were computed by least square fitting of low yield composition data according to one of the classical relations shown below [17][18][19].…”

Section: Resultsmentioning

confidence: 99%

Self-Assembly of Methacrylic Nanostructured Copolymers Containing Polyhedral Oligomeric Silsesquioxanes

et al. 2007

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Two hybrid copolymer series obtained by free-radical copolymerization of methacrylcyclohexyl Polyhedral oligomeric silsesquioxane (POSS) with butyl methacrylate or 2-ethylhexylmethacrylate were characterized by 1 H-NMR spectroscopy, gel permeation chromatography (GPC), X-rays Diffraction (XRD), differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA). Reactivity ratios were calculated by low yield composition data suggesting the formation of random copolymers with low probability of poly-POSS sequences. XRD studies showed the crystallization behaviour of the inorganic phase independently on the POSS content; however sample processing by solvent casting effectively hindered the copolymer self-assembling ability. DSC suggests the formation of polyphasic structures with T g increasing with POSS content, and with endothermal peaks occurring at higher temperature. Finally TGA shows an improved thermal stability of hybrid copolymers with char yield correlated to the level of inorganic phase.

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“…The monomer reactivity ratios of VCA and VIMA in the graft copo~ymer~zat~on on LDPE films in methanol were e~t i m a t e d~~-~' b y the graphical method according to the Kelen-Tudos ( KT) 40 equation, using the results given in Table 111. (2.0 mol/L), the grafting yield on the LDPE films decreased almost linearly with the increase of the VCA content in the solution (as seen in Fig.…”

Section: Graft Copolymerization Of Mixtures Of Vca and Vimamentioning

confidence: 99%

“…The monomer reactivity ratios were calculated as rl (VCA) = 0.024 f 0.001 and rZ(V1MA) = 3.59 k 0.11, respectively, on the basis of a plot of 9 vs. 6 according to the Kelen-Tudos eq. ( 3 ) , 40 using the results from Table IV (Fig. 5).…”

Section: Graft Copolymerization Of Mixtures Of Vca and Vimamentioning

confidence: 99%

Investigations on vinylene carbonate. IV. Radiation induced graft copolymerization of vinylene carbonate and N‐vinyl‐N‐methylacetamide onto polyethylene films

Chen

Does

Bantjes

1992

J of Applied Polymer Sci

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SYNOPSISGraft copolymerization of binary mixtures of vinylene carbonate (VCA) and N-vinyl-Nmethylacetamide (VIMA) onto low density polyethylene (LDPE) films was studied by the mutual y-irradiation technique. Sufficient amounts of functionally active VCA groups could be grafted onto the surface and the hydrophilicity of the surface was also improved. The grafting of VCA onto polyethylene films in the binary solutions was found to be promoted by the presence of VIMA, thus showing a positive synergism. The VCA content in the graft copolymers was always higher than in the copolymers obtained by homogeneous copolymerization using the same monomer feed composition. The monomer reactivity ratios, as well as a preferential partitioning of the monomers surrounding the polymeric substrate, were considered to explain the grafting reactions in the binary systems. INTRODUCTIONSurface modification of polymers has received a great deal of attention during the last decades since it could bring about specific surface properties including adhesion, printability, nonthrombogenicity, and antistatic properties, among others.Since the major problems for application of biomaterials that contact blood occur at the blood-material interface, much research has focused in recent years on the creation of biocompatible surfaces. Grafting of monomers makes it possible to introduce a wide variety of properties on the surface.As suggested by Andrade et al.,' hydrogels are highly blood compatible because of their low interfacial energy when in contact with blood. Hydrogels and hydrophilic surfaces have been developed by graft polymerization of hydrophilic monomers, such as 2-hydroxyethyl methacrylate (HEMA) , N-vinylpyrrolidone ( NVP ) , or acrylamide ( AAm) , [2][3][4][5][6] onto hydrophobic polymers. The grafted substrates showed an improved blood compatibility as compared with the nongrafted polymeric supports. It has been proved that the biological endothelium owes its nonthrombogenic character to its negative charge so that it is obvious that the chemical group distribution involving polar and nonpolar components plays a significant role in blood ~ompatibility.~ In addition, a particular ratio of hydrophilic to hydrophobic sites on a surface may be important for optimal blood c~rnpatibility.~,~ Attempts have been made to elucidate the interrelationship between the hydrophilic-hydrophobic composition of a polymeric material and the biological interactions with that material by graft copolymerization of mixtures of hydrophilic monomers, such as HEMA, and hydrophobic monomers, such as ethyl methacrylate (EMA) , onto a polymeric matrix."*"On the other hand, as combinations of polymeric materials with physiologically active substances, such as heparinI2 and prostaglandin, l3 which inhibit fibrin deposition, or fibrinolytic enzymes, such as urokinase, l4 have exhibited a good blood compatibility, some efforts have been made to functionalize the polymeric surface with reactive groups for further immobilization of bioactive agents. Glycidyl methacr...

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Analysis of the linear methods of determining copolymerization reactivity ratios, 9. Penultimate systems with r₂ = 0

Cited by 145 publications

References 14 publications

Uma revisão sobre os processos de polimerização em suspensão

Uma revisão sobre os processos de polimerização em suspensão

Self-Assembly of Methacrylic Nanostructured Copolymers Containing Polyhedral Oligomeric Silsesquioxanes

Investigations on vinylene carbonate. IV. Radiation induced graft copolymerization of vinylene carbonate and N‐vinyl‐N‐methylacetamide onto polyethylene films

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Analysis of the linear methods of determining copolymerization reactivity ratios, 9. Penultimate systems with r2 = 0

Cited by 145 publications

References 14 publications

Uma revisão sobre os processos de polimerização em suspensão

Uma revisão sobre os processos de polimerização em suspensão

Self-Assembly of Methacrylic Nanostructured Copolymers Containing Polyhedral Oligomeric Silsesquioxanes

Investigations on vinylene carbonate. IV. Radiation induced graft copolymerization of vinylene carbonate and N‐vinyl‐N‐methylacetamide onto polyethylene films

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Analysis of the linear methods of determining copolymerization reactivity ratios, 9. Penultimate systems with r₂ = 0