Degré de polymérisation | EPFL Graph Search

Le degré de polymérisation (DP) définit la longueur d'une chaîne polymère. DP est le nombre d'unités monomères (unités répétitives) constitutives de cette chaîne. Le degré de polymérisation est directement proportionnel à la masse molaire du polymère. Il est exceptionnel qu’un polymère synthétique soit formé de chaînes de même degré de polymérisation, on a plutôt une distribution de chaînes de longueurs différentes ; on parle plus précisément de degré de polymérisation moyen en nombre, \overline{DP}_n ou \overline{X}_n. Il est égal au rapport de la masse molaire moyenne en nombre du polymère à la masse molaire de l'unité monomère, soit : :\overline{DP}_n= \frac { \overline{M}_n} { M_0}. Si le degré de polymérisation est compris entre 2 et quelques dizaines, les chaînes sont appelées oligomères. Influence sur les propriétés physiques Les propriétés spécifiques de l'état macromoléculaire (par opposition à

Synthesis and Postpolymerization Modification of Fluorine-End-Labeled Poly(Pentafluorophenyl Methacrylate) Obtained via RAFT Polymerization

Claudia Battistella, Jie Chen, Harm-Anton Klok

Chain-end-labeled polymers are interesting for a range of applications. In polymer nanomedicine, chain-end-labeled polymers are useful to study and help understand cellular internalization and intracellular trafficking processes. The recent advent of fluorescent label-free techniques, such as nanoscale secondary ion mass spectrometry (NanoSIMS), provides access to high-resolution intracellular mapping that can complement information obtained using fluorescent-labeled materials and confocal microscopy and flow cytometry. Using poly(N-(2-hydroxypropyl)methacrylamide) (PHPMA) as a prototypical polymer nanomedicine, this paper presents a synthetic strategy to polymers that contain trace element labels, such as fluorine, which can be used for NanoSIMS analysis. The strategy presented in this paper is based on reversible addition fragmentation chain transfer (RAFT) polymerization of pentafluorophenyl methacrylate (PFMA) mediated by two novel chain-transfer agents (CTAs), which contain either one (alpha) or two (alpha,omega) fluorine labels. In the first part of this study, via a number of polymerization experiments, the polymerization properties of the fluorinated RAFT CTAs were established. F-19 NMR spectroscopy revealed that these fluorinated RAFT agents possess unique spectral signatures, which allow to directly monitor RAFT agent conversion and measure end-group fidelity. Comparison with 4-cyanopentanoic acid dithiobenzoate, which is a standard CTA for the RAFT polymerization of PFMA, revealed that the introduction of one or two fluorine labels does not significantly affect the polymerization properties of the CTA. In the last part of this paper, a proof-of-concept study is presented that demonstrates the feasibility of the fluorine-labeled poly(pentafluorophenyl methacrylate) polymers as platforms for the postpolymerization modification to generate PHPMA-based polymer nanomedicines.

2018

Reaction injection pultrusion of PA12 composites: Process and modelling

Pierre-Etienne Bourban, Jan-Anders Månson

The development of a reactive pultrusion process is presented by considering the advantages of an in situ polymerisation of thermoplastic lauryllactam monomers. The specifics of the reaction injection unit, of the fibre-drying oven and of different pultrusion dies are given. Models were developed for the optimisation of the pultrusion process and for each processing step, namely: impregnation, polymerisation and cooling. Their individual influence on the overall pultrusion line speed was established. Heat transfer equations were solved in association with polymerisation kinetics and rheology results. Temperature profiles, conversion degrees, and viscosity changes were predicted versus composite part thickness and versus the position along the pultrusion line. Optimal mould lengths can thus be determined for optimum impregnation, polymerisation and cooling. A processing window has been defined in terms of pultrusion line speed and mould temperature. These results demonstrated with the production of profiles that reaction injection pultrusion of PA12 composites can be envisaged at larger scale.

2003

Synthesis and Postpolymerization Modification of Fluorine-End-Labeled Poly(Pentafluorophenyl Methacrylate) Obtained via RAFT Polymerization

Claudia Battistella, Jie Chen, Harm-Anton Klok

2018