Percentage of Rigid Chain-length, a New Concept for Predicting Glass-transition Temperatures and Melting-points of Poly(aryl Ether Ketone)s and Poly(aryl Ether Sulfone)s

Molecular design, microstructure, and physical properties of polymers are strongly related to each other. A better understanding of their interdependence will give the polymer chemist useful ideas for the synthesis of new macromolecules. The present paper aims to compare the thermal behavior of aryl polycondensates based on ether, sulfone, and ketone links. Ultimately the objective is to design a new polymer combining, for example, the glass transition (T(g)) of poly(ether sulfone)s and the crystallinity of poly(ether ether ketone)s. By the use of a new concept the percentage of rigid chain length, it is demonstrated that one can predict T(g) and T(m) of poly(aryl ether ketone)s and T(g) of poly(aryl ether sulfone)s. The feasibility of crystalline poly(aryl ether sulfone)s is also discussed on the basis of the same principle

Glass-transition Temperature of Cross-linked Poly(ether Sulfone)s

A series of crosslinkable maleimide-ended poly(ether sulfone)s has been prepared using a range of molecular masses. The effect of the crosslinking reaction on the glass transition temperatures (T(g)s) is observed. In the range of molecular masses studied, the T(g)s after crosslinking are predominantly dependent on the intrinsic nature of the polymer and are not dependent on the final crosslink density. However, T(g)s of partially crosslinked polymers are related to the concentration of chain-ends consumed by the crosslinking reaction

About the Synthesis of a High-temperature, Crystalline Poly[aryl Ether(ketone-co-sulfone)] .2. Model Compounds Study

From a detailed study of the syntheses and physical properties of semicrystalline poly[aryl ether(ketone-co-sulfone)] model compounds, this paper leads to a better understanding of the chemistry of the polymer synthesis and of its thermal behaviour. Long, crystallizable sequences are shown to arise from the heterogeneous nature of the synthesis. These sequences are responsible for the high melting points observed. Conclusions are drawn on the necessity for a revision of the synthesis procedure in order to avoid the appearance of such sequences

Nucleophilic Cleavage of Activated Aryl Ethers By a Fluoride Anion

The nucleophilic cleavage of differently activated aryl ethers by a fluoride anion is studied. Two sulphone groups in para positions to the ether link appear to activate this sufficiently to allow its nucleophilic substitution by F- to occur from 280-degrees-C upwards. No reaction is observed up to 300-degrees-C when two ketone links are para to the ether, whilst the reaction occurs from 300-degrees-C upwards in the case of a mixed sulphone-ketone activation

About the Synthesis of a High-temperature, Crystalline Poly[aryl Ether(ketone-co-sulfone)] .1. Synthetic Reactions Study

The synthesis of a new poly[aryl ether(ketone-co-sulfone)] proceeds through a chemical mechanism similar to that in the poly(ether ether ketone) and poly(ether sulfone) polymerizations. It is basically a nucleophilic substitution of a dihalogenated species by two alkaline bisphenates. This paper considers the possibility of the occurrence of some side reactions previously observed during the synthesis of poly(ether ether ketone), poly(ether ketone) or poly(ether sulfone). Unwanted nucleophilic substitutions either by phenates (transetherifications) or by fluoride or hydroxyl anions are considered. Their effectiveness during the copolymer synthesis is demonstrated by different techniques and their influence on the final sequence distribution in the chain is discussed

Characterization of Novel Modified Amorphous Poly(ether Sulphone)s

New high-temperature amorphous polymers with chlorine, amine, and maleimide chain-ends have been synthesized by nucleophilic polycondensation and fully characterized by C-13-NMR,H-1-NMR, and potentiometric titration. From chain-end determination, number average molecular masses were calculated. It was confirmed that transetherification during the synthesis led to a randomized polymer of the monomer residues. For nominally amine-ended polymers obtained by addition of m-aminophenol at the end of the synthesis, a small amount of hydroxyl chain-ends was observed. This is ascribed also to transetherification. Complete reaction of the amine chain-ends with maleic anhydride was demonstrated. Reaction of hydroxyl chain-ends with acetic anhydride was also observed. The thermal stability of these different polymers was investigated; lower thermal stability was observed for amine and maleimide-ended polymers. By two different methods, a T-g around 270 degrees C was determined for these novel amorphous aromatic polymers. (C) 1994 John Wiley & Sons, Inc

Raman spectroscopy determination of the thermoplastic content within epoxy resin-copolyethersulfone blends

The possibility of using Raman spectroscopy to determine the local thermoplastic content within blends of epoxy resins and copolyethersulfone was studied. The required calibration of the Raman data is presented here. It was obtained by multivariate methods and was based on homogeneous samples of known content in amine-ended thermoplastic (expressed in weight %). Blends cured with two types of diamine curing agents were separately studied, the curing agents being the methylene bis(2,6-diethylaniline) (MDEA) and the 4,4'diaminodiphenylsulfone (DDS). Partial least-squares (PLS) regressions with external validation were performed. With MDEA, root mean square error of prediction (RMSEP) values at validation were 3.2, 3.7, and 3.0% (depending on the spectral pre-treatment and on the wavenumber selection). RMSEP values were 2.4 or 3.0% with DDS (depending on the wavenumber selection). The applicability of the calibrations to blends containing chlorine-ended copolyethersulfone is discussed. Results obtained with small or large Raman confocal holes are also compared

Phase separation in epoxy-copolyethersulphone blends: morphologies and local characterisation by micro-Raman spectroscopy

This study was aimed at using micro-Raman spectroscopy for the local characterisation of phase separated blends based on epoxy polymer and copolyethersulphone thermoplastic. The morphologies developed in the blends containing 25% by weight of thermoplastic were studied. The calibrations of the Raman data for the determination of the copolyethersulphone content and the epoxide conversion are presented in this paper and their applicability for spatially resolved Raman characterisation discussed. From spectra collected in both phases after increasing cure times, the evolution of the copolyethersulphone content in each phase was quantitatively determined, whilst a qualitative evolution of the epoxide conversion was obtained. To our knowledge, this study provided for the first time direct measurements of phase characteristics in thermoset-thermoplastic blends. (C) 2003 Elsevier Science Ltd. All rights reserved

The use of Raman spectroscopy to study the reaction between an amine-terminated thermoplastic and epoxy resins

Reactive thermoplastics are increasingly used as toughening modifiers for epoxy resins. A way to understand the influence of the reactive end-groups on the toughening and curing mechanisms is to observe in situ the reaction between the thermoplastic and the growing epoxy network. For this purpose, Raman spectroscopy has been used to follow the reaction of aromatic amines with epoxide monomers through the evolution of an amine-substituted aromatic vibration. A double shift of this peak was correlated with the formation of secondary and tertiary amines. Band assignment was confirmed by the study of model compounds. Through this method, qualitative observation of the reaction between an amine-ended copolyethersulphone thermoplastic and epoxide was performed. Unfortunately, in the studied blend containing the curing agent, a band appearing upon curing overlapped with the band characterising the end-group reaction. (C) 2000 Elsevier Science Ltd. All rights reserved

Raman spectroscopy and DSC determination of conversion in DDS-cured epoxy resin: Application to epoxy-copolyethersulfone blends

Methods have been developed to determine by Raman spectroscopy the epoxide conversion in a 4,4'-diaminodiphenylsulfone (DDS)cured epoxy resin as well as in blends of this resin with copolyethersulfone thermoplastic. The proposed spectral treatments consisted of a peak ratio method and of multivariate analysis. The Raman data were first successfully calibrated on the basis of neat resin samples with the use of the values of epoxide conversions provided by differential scanning calorimetry (DSC) measurements. The use of DSC as a reference technique is discussed, In order to be applied to blends of the same epoxy resin and reactive copolyethersulfone, the calibrations were based on spectral data that would not be influenced by the presence of this thermoplastic. The blend samples were homogeneous at the scale of the Raman laser focusing. The epoxide conversions deduced from the Raman and the DSC results were compared for these blends. Limitations associated with both techniques are discussed