Synthesis of some low glass transition temperature polytetrahydrofuran polymers
TL;DR: In this paper, the polymerization of tetrahydrofuran with boron trifluoride ethereate in three steps was described, and the resulting polymers were characterized by molecular weight, hydroxyl number, amine equivalent and i.r., viscosity and density measurements.
About: This article is published in European Polymer Journal.The article was published on 1989-01-01. It has received 10 citations till now. The article focuses on the topics: Polytetrahydrofuran & Polymer.
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TL;DR: In this paper, the chemistry, types, and synthesis of polyurethanes (PUs) are discussed, with a specific emphasis on their recyclability and recoverability, and information is provided on the environmental friendliness of the PU.
Abstract: Polyurethanes (PUs) are a class of versatile materials with great potential for use in different applications, especially based on their structure–property relationships. Their specific mechanical, physical, biological, and chemical properties are attracting significant research attention to tailoring PUs for use in different applications. Enhancement of the properties and performance of PU-based materials may be achieved through changes to the production process or the raw materials used in their fabrication or via the use of advanced characterization techniques. Clearly, modification of the raw materials and production process through proper methods can produce PUs that are suitable for varied specific applications. The present study aims to shed light on the chemistry, types, and synthesis of different kinds of PUs. Some of the important research studies relating to PUs, including their synthesis method, characterization techniques, and research findings, are comprehensively discussed. Herein, recent advances in new types of PUs and their synthesis for various applications are also presented. Furthermore, information is provided on the environmental friendliness of the PUs, with a specific emphasis on their recyclability and recoverability.
861 citations
TL;DR: In this article , the authors present a framework governing the development of an efficient, accurate, and transferable coarse-grained (CG) model of a polyether material by integrating machine learning (ML) with optimization algorithms.
Abstract: Abstract This work presents a framework governing the development of an efficient, accurate, and transferable coarse-grained (CG) model of a polyether material. The framework combines bottom-up and top-down approaches of coarse-grained model parameters by integrating machine learning (ML) with optimization algorithms. In the bottom-up approach, bonded interactions of the CG model are optimized using deep neural networks (DNN), where atomistic bonded distributions are matched. In the top-down approach, optimization of nonbonded parameters is accomplished by reproducing the temperature-dependent experimental density. We demonstrate that developed framework addresses the thermodynamic consistency and transferability issues associated with the classical coarse-graining approaches. The efficiency and transferability of the CG model is demonstrated through accurate predictions of chain statistics, the limiting behavior of the glass transition temperature, diffusion, and stress relaxation, where none were included in the parametrization process. The accuracy of the predicted properties are evaluated in context of molecular theories and available experimental data.
5 citations
TL;DR: In this paper, an easy and convenient one-pot procedure is described to prepare iodo-, azido-, and amino-terminated PTHF with minimal use of hazardous chemicals.
Abstract: Polytetrahydrofuran (PTHF) is a very widespread polymer, which is used in numerous applications. Very frequently, its functional end groups play a key role, in that they are exploited to perform further reactions. However, only limited work is available to date on the preparation of functionalized PTHF, mostly using hazardous compounds. Here, an easy and convenient one-pot procedure is described to prepare iodo-, azido-, and amino-terminated PTHF with minimal use of hazardous chemicals. This is thought to be the first example of iodo- and azido-terminated PTHF. Additionally, a novel alternative method to obtain bromo- and cyano-terminated PTHF is reported.
5 citations
TL;DR: In this paper, a cationic ring-opening copolymerization of THF with cyano ethylene oxide (CEO) was conducted with methyl trifluoromethanesulfonate (MeOTf) as an initiator.
Abstract: Cyano-functional polyether copolymers based on THF were prepared via cationic ring-opening copolymerization of THF with cyano ethylene oxide (CEO). The CEO content of poly(tetrahydrofuran) (polyTHF) based copolymers varied from 3.3 to 29.3%, and molecular weights ranged from 5100 to 31900 g·mol–1 with Mw/Mn in the range of 1.31 to 1.74 (SEC in THF, PS standards). The polymerization was conducted with methyl trifluoromethanesulfonate (MeOTf) as an initiator. Kinetic studies concerning incorporation of both monomers were performed via NMR spectroscopy. The cyano groups at the poly(THF-co-CEO) copolymers enable direct access to amino (polyTHF–NH2) and carboxyl groups (polyTHF–COOH) in facile one-step procedures, respectively. The modified copolymers were characterized via NMR, MALDI–ToF mass, and FT-IR spectroscopy. Thermal properties of the materials were studied via differential scanning calorimetry (DSC), demonstrating a gradual decrease of the melting points with increasing amount of CEO in the copolymer...
5 citations
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TL;DR: In this paper, it was shown that polyisobutylene can form a glass, with the same transitions in thermal properties characteristic in the vitrification of substances of low molecular weight.
Abstract: Polyisobutylene, with an average molecular weight of about 4900, is at room temperature a highly viscous liquid. When cooled, it has been found to form a glass, with the same transitions in thermal properties characteristic in the vitrification of substances of low molecular weight. The heat capacity of polyisobutylene has been measured from 118°K to 295°K. It increases by 32 percent between 192°K and 202°K. The thermal expansion coefficient of polyisobutylene has been measured from 160°K to 300°K. It increases by 200 percent between 185°K and 205°K. The mean temperature of transition corresponds to a viscosity of about 1013 poises, in agreement with a rule observed generally for glass‐forming materials. The factors on which the transition temperature depends are discussed.
39 citations
TL;DR: In this paper, the intrinsic viscosity vs. molecular weight relationship obtained in the range of molecular weight from 3.5·104 to 1.1·106 were investigated, where the conformational parameter σ was defined as the ratio of the end-to-end distance of the polymer in the unperturbed state to that in the freely rotating state.
Abstract: Viscosity and light scattering measurements of poly(tetrahydrofuran) were carried out in various solvents, involving a mixed theta solvent. The intrinsic viscosity vs. molecular weight relationships obtained in the range of molecular weight from 3.5·104 to 1.1·106 were : [η] = 1.31·10−3 Mw0.60 in benzene (30°C.), 1.76·10S−3Mw0.54 in a mixed theta solvent of ethyl acetate (22.7 wt.-%) and n-hexane (77.3 wt.-%) (31.8°C.), repectively. The recent x 3 treatment of the viscosity data lead to the following values of the conformational parameter σ which was defined as the ratio of the end-to end distance of the polymer in the unperturbed state to that in the freely rotating state: σ = 1.85 in benzene, 1.70 in cyclohexane. 1.58 in ethyl acetate, and 1.64 in the theta mixture. Effect of benzene on the chain conformation was notable. This polymer was prepared by bulk polymerization at 0°C. with an aluminium triethyl and water catalyst and the ratio of the weight average to the number average molecular weights was about 1.04 as was determined by the sedimentation velocity analysis.
In verschiedenen Losungsmitteln, unter denen sich ein Θ-Losungsmittelgemisch befand wurden Viskositats- und Lichtstreuungsmessungen an Polytetrahydrofuranen ausgefuhrt. Wir bestimmten folgende [η]-M-Beziehungen in einem Molekulargewichtsbereich von 3,5·104 bis 1,1·106:
[η] = 1,31·10−3M20.60 in Benzol (30°C), 1,76·10−3Mw0,54 in Cyclohexan (30°C), 4,22·10−4Mw0,65 in Athylacetat (30°C) und 3,43·10−3Mw0,45 in einem Θ-Losungsmittelgemisch aus Athylacetat (22,7 Gew.−%) und n-Hexan (77,3 Gew.-%) (31,8°C).
Die Auswertung der Viskositatsmessungen nach einer kurzlich vorgeschlagenen α3-Beziehung lieferte folgende Werte fur den Konformationsparameter σ, der als das Verhaltnis des Fadenendenabstandes des Polymeren im ungestorten Zustand zu dem Fadenendenabstand bei freier Drehbarkeit definiert ist : σ = 1,85 in Benzol, 1,70 in Cyclohexan, 1,58 in Athylacetat und 1,64 in der Θ-Mischung. Bemerkenswert ist der Effect des Benzols auf die Kettenkonformation.
Das Polymere wurde bei 0°C durch Polymerisation in Substanz mit einem Aluminium-triathyl-Wasser-Katalysator hergestellt. Das Verhaltnis des Gewichtsmittels zum Zahlenmittel des Molekulargewichts wurde durch Analyse der Sedimentationsgeschwindigkeit zu etwa 1,04 bestimmt.
38 citations
21 citations
TL;DR: In this article, seven variables were investigated to determine their effect on the physical and mechanical properties of isocyanate-terminated polyurethane prepolymers, and the choice of catalyst along with the ratio of diol to triol was found to most significantly control the prepolymer properties.
Abstract: Using statistically designed experiments, seven variables were investigated to determine their effect on the physical and mechanical properties of isocyanate-terminated polyurethane prepolymers. The choice of catalyst (dibutyltin diacetate, T-1, or stannous octoate, T-9) along with the ratio of diol to triol were found to most significantly control the prepolymer properties. Other variables such as reaction temperature, reaction time, and order of polyol addition did not affect the system. In comparing the two catalysts, T-9 was found to be concentration sensitive, yielding low-viscosity prepolymers at the lower catalyst level and higher viscosity, unstable materials at the higher catalyst level. No evidence was found to show concentration sensitivity of T-1. A series of prepolymers based on varying ratios of diol to triol were synthesized, and their physical and mechanical properties are reported.
12 citations
TL;DR: In this article, the properties of isocyanate-terminated polyurethane prepolymers were optimized through the use of statistically designed experiments using a simple 2 × 2 factorial with centerpoint statistical design.
Abstract: The properties of isocyanate-terminated polyurethane prepolymers were optimized through the use of statistically designed experiments. A simple 2 × 2 factorial with centerpoint statistical design was used to determine the effect the diol-to-triol ratio and per cent free isocyanate had on the viscosity of the prepolymer. Combinations of a 1000 or 2000 molecular weight diol with either a 1500 or 4100 molecular weight triol showed that a reasonable range of viscosity could be maintained only with the 4100 molecular weight triol. A nine-point design was then utilized to predict the best levels of free isocyanate and polyol ratio that would yield cured urethane polymers with the highest tensile strengths, moduli, and elongations. With this design, second-order equations were computed that predict the mechanical responses of urethane polymers based on the free isocyanate and polyol ratio used in its formulation.
4 citations