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TheLink Report Summary

Project ID: 642890
Funded under: H2020-EU.1.3.1.

Periodic Reporting for period 1 - TheLink (European Training Network to Accelerate the Development Chain of Nanostructured Polymers)

Reporting period: 2014-11-01 to 2016-10-31

Summary of the context and overall objectives of the project

TheLink aims to provide interdisciplinary training to 15 ESRs covering the entire development chain for nanostructured polymers. The development of nanostructured materials for 3 case studies (phase separated polymers, separation membranes and conductive polymer composites) is advanced through closely interlinked PhD projects in the disciplines of simulation, production and characterization.
This interdisciplinary approach is important as several steps, spanning various disciplines, are needed from the concept of a nanostructured material and the generation of a desired functionality through to the final product. Often, the specialized focus of university education does not provide the necessary space to examine adjacent disciplines.
The development of functional nanostructured polymers will pave the way towards new products that are competitive in a globalized world. The faster the innovation cycles, the greater the competitiveness of the European industry. TheLink’s ESRs will gain the interdisciplinary skills needed for effective innovation in this key development field.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Electrically conductive composites:
Simulation techniques help establish correlations between the nano- and microstructure of materials and their macroscopic properties e.g. electrical conductivity, EMI shielding, optical and mechanical properties. The simulation techniques are based on models, which were developed, improved and applied in TheLink. On an atomic scale, the chemical functionalization of CNTs helps improve their interaction with the embedding matrix. For this purpose, the load transfer between functionalized CNTs and a polyethylene matrix was calculated using a hybrid approach combining quantum mechanical methods and classical molecular dynamics. On a mesoscopic scale, a 3D model was elaborated which is useful for calculating the conductivity, the EMI shielding and the optical properties, describing the composite as a resistor/capacitor network. The effective conductivity of polymer/CNT composites at larger length scales, together with mechanical and strain-sensing capabilities, was calculated using a finite element analysis based on representative volume elements.
The cost effective characterization of the nano- and microstructure of composites is an unsolved problem. Measurement of the dielectric properties and the use of optical coherence tomography (OCT) have the potential to overcome this. A model for the description of the effective dielectric properties of 2 phase materials, depending on the volume fraction of the phases, particle aspect ratio and particle orientation, was elaborated and experimentally verified. The speed, robustness and compactness, as well as the measurement accuracy and sensitivity of an OCT system was significantly improved by using chip-scale frequency comb generators as optical sources and by dedicated signal processing techniques. Reference measurement techniques were applied, also to evaluate material compatibility with the techniques, and further developed. Polarized Raman spectroscopy, SEM, FIB-SEM and 3view-SEM including the use of advanced preparation techniques like plasma etching were applied.
The production of conductive composites based on CNTs and graphene was also addressed. The percolation curves of graphene in epoxy, PVC plastisol, PP and PA6 were determined. TPU/graphene composites with different reduced graphene oxides were produced and characterized to study the effect of oxygen content. The production process for graphene oxide was improved to minimize defects. For the spatial orientation of CNTs in media with low viscosity due to electric fields, experimental setups were built to produce composite samples. Various matrix/filler systems were tested with a wide range of processing parameters. To access the electromagnetic interference (EMI) shielding effectiveness (SE) of conductive polymer composites, produced by injection moulding, a measurement setup was designed and validated using electromagnetic wave FEM simulation software. Preliminary EMI SE measurements of injection moulded polycarbonate/carbon nanotubes (PC/CNTs) composites were carried out.
Separation membranes:
Wearable artificial kidneys are highly desirable for the comfort of dialysis patients but require highly sophisticated separation membranes. The modelling of membranes can accelerate their development to achieve the necessary separation/removal performance and the flux through the membrane. For this purpose a 3D computer simulation model of a membrane with an attached cell monolayer of immortalized living proximal tubule epithelial cells (ciPTEC) was built using the Comsol Multiphysics software. The stochastic porous topology of a mixed matrix membrane was generated by an algorithm. Property calculations taking into account the toxin transport through MMMs and the adsorption of the toxin on the embedded sorbent were performed. To produce dialysis membranes two strategies are followed: (i) chitosan-based adsorbents incorporated as particles in MMM and (ii) positively charged nanofiltration membranes. To remove endotoxins a further concept consisting of MMM composed of activated carbons which are dispersed in a polymeric matrix was developed. Furthermore PVDF hydrophilic and hydrophobic membranes using non-solvent induced phase separation are being developed and a hydrophilic PES membrane was optimized, produced by vapor induced phase inversion.
Phase separated polymers:
A model for simulation of the formation of phase separated polymers was developed using quantum chemistry, molecular dynamics and mesoscopic simulation methods. The viscosity, density and the measured IR spectra of the precursor alkyl-diiscocyanurate trimers (ADI) could be predicted with a good accuracy. Mono- and diisocyanate trimers with 4-7 carbon atoms in the isocyanate structures were synthesized as precursors of phase separated polyurethanes. Viscosity studies of various monomer HDI-trimers and derivatives were carried out and the findings could be explained on the basis of simulations. The processing and analysis of HDI-trimer based network structures was initiated.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

In simulation, new models for different types of composites were developed, partially by the combination of several simulation techniques over various length scales or by the use of 3D models of the microscopic structure of materials derived from measurements of the real material structure.
For newly synthesized chemical species useful as precursors for the production of phase separated polymers, the density, the optical behavior and viscosity could be predicted with a high accuracy.
Models for predicting the removal of specific species from blood by porous membranes and mixed matrix membranes were developed and tested by initial calculations.
In the area of characterization, measurement techniques were improved in view of their accuracy (OCT) or successfully applied to various material combinations (SEM and polarized Raman spectroscopy). Measurement setups were built up for EMI shielding and dielectric properties.
In the area of processing, several setups for the spatial orientation of nanostructures in the composites were built and successfully tested for low viscous matrix systems. New insights about the influence of processing parameters and the oxidation state of graphenes on the mechanical, thermal and electrical properties of their thermoplastic and thermoset composites were achieved.
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