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A comprehensive study was undertaken to obtain a more fundamental understanding of the phase behavior of the p-DTS(FBTTh2)2:PC71BM system, used in small molecule organic solar cells, with a strong focus on the amorphous phase and its influence on crystallinity. Three dedicated thermal protocols were used in combination with advanced thermal analysis, solid-state NMR, and wide-angle X-ray diffraction. Rapid cooling, to avoid structure formation and gain insight in the amorphous phase, and slow cooling, to promote structure formation, were used as limiting cases to explain the intermediate behavior after device processing from solution. A complete state diagram was developed, and the glass transition (Tg)–composition relationship was determined. In the case of slow cooling and the procedure used for device processing, the rapid crystallization of p-DTS(FBTTh2)2 leads to an enrichment of the amorphous phase in PC71BM, increasing its Tg and causing vitrification of the mixed amorphous phase before crystallizationwhen the total amount of PC71BM exceeds 70 wt %. The common processing additive 1,8-diiodooctane (DIO) was found to lead to a lower p-DTS(FBTTh2)2 crystallinity and smaller average crystal size. More importantly, it acts as a strong plasticizer, lowering Tg significantly and thus reducing the morphological stability of the p-DTS(FBTTh2)2:PC71BM mixtures.

After its introduction by Mike Reading and TA Instruments in 1992 [1], modulated temperature differential scanning calorimetry (MT-DSC) became a hot topic in thermal analysis [2]. Almost three decades later, the technique is still a bit of a mystery to some. The aim of this presentation is to give insight in the underlying principles of the technique and the signals obtained, its capabilities and limitations, and some of its main applications.

This work aims to calculate the rigidity point temperature of aluminum alloys by three new methods and compare them with currently employed methods. The influence of major and minor alloying elements over the rigidity point temperature is also discussed. Until now it has been difficult to determine the exact temperature of the rigidity point, since small variations in the data obtained give variable results, making it difficult to automate the process with high accuracy. In this work we suggested three new mathematic methods based on the calculation of higher order derivatives of (dT/dt) with respect to time or temperature compared to those currently employed. A design of experiments based on the Taguchi method was employed to compare the effect of the major and minor alloying elements for the AlSi10Mg alloy, and to evaluate the accuracy of each developed method. Therefore, these systems will allow better automation of rigidity point temperature (RPT) determination, which is one of the most important solidification parameters for solidification simulators. The importance of the correct determination of this parameter lies in its relation to quality problems related to solidification, such as hot tearing. If the RPT presents very low-temperature values, the aluminum casting will be more sensitive to hot tearing, promoting the presence of cracks during the solidification process. This is why it is so important to correctly determine the temperature of the RPT. An adequate design of chemical composition by applying the methodology and the novel methods proposed in this work, and also the optimization of process parameters of the whole casting process with the help of the integrated computational modeling, will certainly help to decrease any internal defective by predicting one of the most important defects present in the aluminum industry. This research was partially funded by the Basque Government through the Etorgai Programme 2016, under the Filing Identification Number ZE-2016/00018 and the Elkartek Programme 2020, KK-2020-00047 for research, technological development and demonstration.

A novel hyphenated RheoDSC combines rheological and calorimetric analyses of samples by performing rheological experiments inside a DSC cell. This enables direct studies of the chemorheological changes of epoxy-amine thermosets during crosslinking. The rheological and calorimetric information can be presented in time-temperature-transformation (TTT) cure diagrams, without the need for making interpretations based on experiments performed on different samples in the different thermal environments of individual rheometers and calorimeters. © 2012 Elsevier Ltd. All rights reserved. ispartof: Reactive & Functional Polymers vol:73 issue:2 pages:332-339 status: published

The phase separation behavior of polymer blend thin films of 100–150 nm was studied using differential AC Chip calorimetry. By taking advantage of the low sensor and sample mass inherent to chip calorimetry, a new methodology based on temperature jumps was developed. This methodology allowed the construction of the state diagram of polymer blend thin films as evidenced for two model systems (PVME/PS and PVME/Phenoxy) displaying a lower critical solution temperature behavior. The state diagram in thin films was compared to the one obtained in bulk using Modulated Temperature DSC. In comparison with bulk, a lower phase separation temperature and a broadening of the homogeneous glass transition temperatures is observed for both model systems. This might be an indication of a surface induced ‘destabilization’ by composition gradients which are not present in bulk.

In this work, the phase diagram of poly(3-hexyl thiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) blends is measured by means of standard and modulated temperature differential scanning calorimetry. Blends were made by solvent-casting from chlorobenzene, as blends cast from toluene or 1,2-dichlorobenzene prove to retain effects of phase segregation during casting, hindering the determination of the phase diagram. The film morphology of P3HT/PCBM blends cast from chlorobenzene results from a dual crystallization behavior, in which the crystallization of each component is hindered by the other component. A single glass transition is observed for all compositions. The glass transition temperature (Tg) increases with increasing concentration of PCBM: from 12.1 degrees C for pure P3HT to 131.2 degrees C for pure PCBM. The observed Tg defines the operating window for the thermal annealing and explains the long-term instability of both the morphology and the photovoltaic performance of the P3HT/PCBM solar cells.

Micro-thermal analysis was used for studying interphases formed in particle-filled composites based on an epoxy resin matrix. The subsurface distribution of the particles can be observed in the conductivity images, while spatial variations in thermal properties can be determined by local thermal analyses. For an anhydride-cured epoxy system filled with porous silica particles, an interphase is observed around the particles. In the ca. 60 μm wide interphase, the glass transition temperature gradually decreases from the bulk value to a value about 10 °C lower. The less densely cross-linked interphase can be detected in the thermal conductivity images and in the local thermal analyses. The interphase formation is attributed to the effect of adsorbed water on the polymerisation mechanism.

Bulk-heterojunction (BHJ) organic photovoltaics are based on an active layer consisting of a donor polymer and an acceptor material blend. For an optimal BHJ, this active layer has to form a phase separated co-continuous nanoscale morphology. In practice, thermal treatments (annealing) are often used to obtain the desired morphology. In this work, the thermal transitions and isothermal crystallization kinetics of the P3HT:PCBM (poly[3-hexyl thiophene] : [6,6]-phenyl C61 butyric acid methyl ester) system, a benchmark BHJ system, were studied by Rapid Heating Cooling Calorimetry (RHC) [1,2] and Fast Scanning Differential Chip Calorimetry (FSDCC) [3]. Rapid-scanning thermal analysis techniques like RHC made it possible to restrict the processes that occur during heating or cooling at slower rates (e.g., nucleation), enhancing the study of the effects of an annealing treatment. However, the active layers used in organic photovoltaics, have thicknesses in the order of 100 nm. In this range of layer thicknesses, the transitions and transformations in these layers may be influenced by the presence of the layer-substrate and layer-air interfaces. Fast Scanning Differential Chip Calorimetry permitted for the first time the thermal characterization of the solar cell blends in layers as thin as used in actual organic photovoltaic devices. Due to the very high heating and cooling rates reached in FSDCC (up to 106 K.s-1), it is now also possible to perform a similar study for pure P3HT, which is impossible using more conventional techniques due to its very fast crystallization kinetics.

Bulk-heterojunction (BHJ) organic photovoltaics are based on an active layer consisting of a donor polymer and an acceptor material blend. For an optimal BHJ, this active layer has to form a phase separated co-continuous nanoscale morphology. In practise, thermal treatments (annealing) are often used to obtain the desired morphology. Using advanced fast-scanning thermal analysis techniques has made it possible to avoid the thermal effects that occur during heating or cooling (e.g. nucleation) and only study the effect of an annealing treatment. A drawback of most thermal analysis techniques however, is that they work with bulk materials. The active layers used in organic photovoltaics on the other hand, have thicknesses in the order of 100 nm. In this study, the thermal transitions and isothermal crystallization kinetics of the P3HT:PCBM (poly[3-hexyl thiophene] : [6,6]-phenyl C61 butyric acid methyl ester) system, a benchmark BHJ system, was studied by Rapid Heating Cooling Calorimetry (RHC) [1,2] and Fast Scanning Differential Chip Calorimetry (FSDCC) [3]. This allows for thermal characterization of the blend in bulk and, for the first time, in thin layers as used in actual organic photovoltaic devices. Due to the very high scanning rates reached in FSDCC, it is now also possible to perform a similar study of pure P3HT, which is impossible using more conventional techniques due to its very fast crystallization kinetics. [1] R.L. Danley, P.A. Caulfield, S.R. Aubuchon, American Laboratory 40 (2008) 9. [2] F. Demir, N. Van den Brande, B. Van Mele, S. Bertho, D. Vanderzande, J. Manca, G. Van Assche, J. Therm. Anal. Calorim., 105 (2011) 845. [3] A.A. Minakov, A.W. van Herwaarden, W. Wien, A. Wurm, C. Schick, Thermochim. Acta, 461 (2007) 96.

Organic photovoltaics using the bulk-heterojunction (BHJ) concept are based on an active layer consisting of a donor polymer and an acceptor material blend. For an optimal BHJ, this active layer should phase separate into a co-continuous nanoscale morphology. By using advanced fast-scanning thermal analysis techniques, it has become possible to avoid the thermal effects that occur during heating or cooling (e.g. nucleation) and only study the effect of an annealing treatment. However, while conventional thermal analysis techniques work with bulk materials, the active layers used in organic photovoltaics have thicknesses in the order of 100 nm. In this study, the thermal transitions and isothermal crystallization kinetics of the P3HT:PCBM (poly[3-hexyl thiophene] : [6,6]-phenyl C61 butyric acid methyl ester) system, a benchmark BHJ system, was studied by Rapid Heating Cooling Calorimetry (RHC) [1,2] and Fast Scanning Differential Chip Calorimetry (FSDCC) [3]. This allows for thermal characterization of the blend in bulk and, for the first time, in thin layers as used in actual organic photovoltaic devices. Due to the high scanning rates reached in FSDCC, it is now also possible to perform an isothermal crystallization study of pure P3HT. [1] R.L. Danley, P.A. Caulfield, S.R. Aubuchon, American Laboratory 40 (2008) 9. [2] F. Demir, N. Van den Brande, B. Van Mele, S. Bertho, D. Vanderzande, J. Manca, G. Van Assche, Journal of Thermal Analysis and Calorimetry 105 (2011) 845. [3] A.A. Minakov, A.W. van Herwaarden, W. Wien, A. Wurm, C. Schick, Thermochimica Acta 461 (2007) 96.

Organic photovoltaics of the bulk-heterojunction type rely on an active layer consisting of a co-continuous morphology of donor and acceptor phases in order to reach their optimum efficiency. In these active layers, the donor is a conjugated polymer, and the acceptor is most often a fullerene derivative. In order to fine-tune the morphology and crystallinity and thus increasing the efficiency a post-production isothermal annealing is performed on these systems before operation [1-2]. An optimal annealing treatment can only be carried out when the thermal transition and annealing kinetics are known for the used active layer. Using advanced fast-scanning thermal analysis techniques, the thermal effects that occur during heating or cooling (e.g. nucleation) can be avoided, making it possible to study only the effects of isothermal annealing. In this study, the thermal transitions and isothermal crystallization kinetics of the P3HT:PCBM (poly(3-hexyl thiophene: [6,6] - phenyl C61 - butyric acid methyl ester) system, a model system for organic photovoltaics, was studied by Rapid Heating Cooling Calorimetry (RHC) [3] and Fast Scanning Differential Chip Calorimetry (FSDCC) [4]. For a thorough simulation of thermal annealing, both isothermal crystallization directly from the molten state and by first cooling to the glassy state were studied. A double bell shaped peak is found for the crystallization rates, obtained by applying the Avrami model on RHC results. However, a clear rate difference between the melt and glass pathways is visible [5]. The higher rates for the glass pathway can be attributed to the effect of nucleation, which was not sufficiently avoided by the scanning rates of RHC. This rate difference is clearly reduced when using the much increased scanning rates allowed by FSDCC, resulting in an effective simulation of isothermal annealing.

PCL-based nanoclay (layered silicate) nanocomposites are prepared using a small scale intermeshing co-rotating twin-screw extruder. Improving the level of nanoclay dispersion in PCL nanocomposites is obtained by changing the extrusion parameters. Increasing the screw speed and decreasing the throughput leads to an improved dispersion quality, as observed from the improved mechanical properties of the nanocomposites as well as from their clearly affected rheological and crystallization behavior. Furthermore, a commercially available software that simulates the twin-screw extrusion process (LUDOVIC) is used to asses the processing parameters applied for making the nanocomposites.

RheoDSC is a novel thermal analysis technique that permits simultaneous rheometry and calorimetry on one sample. By combining two instruments in a single setup, introducing a rotor assembly and an insert for fixing sample plates into the DSC cell, an operational instrument was developed. As design and material selection greatly influence the calorimetric performance of this combined technique, several designs were evaluated through numerical simulation of experiments. Finite element based heat transfer modelling, in some cases combined with chemical reaction modelling, is used to evaluate the quality of the calorimetric response, supporting the instrument design.

Organic photovoltaics (OPVs) are considered a promising energy source for the future, owing to interesting properties such as easy processing and flexibility. Their main drawback however, is the low efficiencies that can be obtained so far. So far the highest OPV efficiencies have been found for so-called bulk-heterojunction (BHJ) solar cells, where the active layer is a bicontinuous composite of donor and acceptor phases. Due to their high electron affinity and ability to transport charge, fullerene derivatives are the most widespread type of acceptor. As a donor phase a conjugated, light-excitable polymer is required. In this study a poly(3-hexyl thiophene) (P3HT) and [6,6]-phenyl C61 - butyric acid methyl ester (PCBM) blend, the most widespread OPV system, is investigated by both experimental and theoretical means. An important technological challenge for BHJ OPV's is the morphology of the active layer. Due to the limited lifetime of generated excitons, a nm-size phase separated morphology is requiredfor efficient charge generation at the interface between donor and acceptor. A more crystalline material will also lead to more efficient charge transfer, and post-production annealing plays an important role in optimising these two factors. In this work, post production annealing is therefore studied using several fast-scanning calorimetry techniques, such as Rapid Heat-Cool Calorimetry (RHC) and Fast Scanning Differential Chip Calorimetry (FSDCC. By applying the Avrami model on the isothermal crystallisation of a P3HT/PCBM 1:1 blend, it is found that the crystallisation rate goes through 2 maxima, making it possible to improve the annealing procedure. Next to the morphology of the active layer, the mechanism of charge transfer and exciton dissociation at the donor/acceptor interface is just as important. This charge transfer is modelled using ab initio DFT calculations under periodic boundary conditions (PBC).

During the processing of polymers, transformations go hand in hand with changes in the thermal and rheological properties. During the crystallization of thermoplastics and the crosslinking polymerization (curing) of thermosets, the heat released is a direct measure of the progress of the transformation, while at the same time the rheology of these materials changes from a (predominantly) liquid to a solid behaviour. The RheoDSC developed by us [1] combines a TA Instruments Q2000 Tzero DSC and AR-G2 rheometer, permitting simultaneous rheological and calorimetric measurements on a sample inside a DSC cell (Fig.1). The design of the RheoDSC instrument and its calibration were supported by heat transfer modelling [2] (Fig.2). Both rheological and calorimetric signals were validated using reference materials. The calorimetric and rheological performance of the RheoDSC is comparable to the standalone instruments. The instrument was explored for (1) studying thermosetting systems, permitting a direct quantification of the gel conversion and the construction of time-temperature-transformation diagrams [3], and for (2) studying the rheological changes during isothermal and nonisothermal crystallization as well as flow-induced crystallization [4].

Bulk-heterojunction organic solar cells rely on an active layer consisting of a co-continuous morphology of donor and acceptor phases in order to reach their optimum efficiency. A conjugated, light-excitable polymer is most often used as an electron donor, and fullerene derivatives are the most widespread type of electron acceptor. Post-production isothermal annealing plays an important role for these systems, both for fine-tuning the morphology and crystallinity and thus increasing the efficiency, but also for retaining the desired morphology during long-term operation. Optimal thermal annealing can only be carried out when the thermal transitions and annealing kinetics for the used systems are known. Using advanced fastscanning thermal analysis techniques, the thermal effects that occur during heating or cooling (e.g. nucleation) can be avoided, making it possible to study only the effects of isothermal annealing. In this study, the thermal transitions and isothermal crystallization kinetics of the P3HT:PCBM (poly(3-hexyl thiophene: [6,6] - phenyl C61 - butyric acid methyl ester) system as used in organic photovoltaics was studied by Rapid Heating Cooling Calorimetry (RHC) and Fast Scanning Differential Chip Calorimetry (FSDCC). In order to simulate thermal annealing in a complete way, both annealing directly from the molten state and by first cooling to the glassy state were studied. From RHC results a double bell shaped peak is found for the crystallization rates, but a clear rate difference between the melt and glass pathways is visible. The consistently higher rates for the glass pathway can be attributed to the effect of nucleation, which was not sufficiently avoided by using RHC. This rate difference is clearly reduces when using the much increased rates allowed by FSDCC, resulting in an effective simulation of isothermal annealing.

Research in the field of materials that are able to repair sustained damage is increasing worldwide. This is also the case for polymers and polymer-based materials, like composites and coatings. Reversible polymer network systems are one type of polymer chemistries that is able to repair a sustained damage. In this work different polymer network systems are made thermally reversible by the incorporation of dynamic covalent bonds in the polymer network structure. The reversibility is based on the Diels-Alder reaction of a furan and a maleimide [1-2]. These reversible polymer network systems can be repaired by increasing temperature. Local thermal analysis techniques have proven themselves very useful to study the thermal properties of polymeric materials on the micro- or even nano-scale. These local techniques can be used to study the healing mechanism and healing kinetics at the microscopic scale and to compare this healing mechanism for different polymer network structures and chemistries [3]. The self-healing behavior is studied on the microscopic scale with local and surface analysis techniques. Atomic Force Microscopy (AFM) and Local Thermal Analysis (LTA) techniques are used to study the thermal properties at the microscopic scale and, ultimately, to reveal the self-healing of microscopic defects. Self-healing polymer networks structures are applied as protective coatings on metallic substrates. Nano-lithography is used to create reproducible microscopic defects with tunable size. The heating-used healing of the defects is monitored by AFM by means of an in-situ heating stage.

In this paper, a combined experimental and theoretical study was performed on the P3HT:PCBM system used in organic photovoltaics. Fast-scanning differential chip calorimetry, an advanced thermal analysis technique, was used to simulate the thermal annealing used in the production of P3HT:PCBM solar cells to increase the degree of crystallinity, and thus efficiency. The main advantage of this technique for stuying the thermal annealing are the very high rates of heating and cooling that can be used, up to 10 6 K.s -1 , permitting one to avoid crystallization during cooling. In parallel with the experimental study, the charge transfer between donor (P3HT) and acceptor (PCBM) at the interface is studied using density functional theory. The charge separation between donor and acceptor present for the ground state of the combined system, diminished when the first triplet was investigated. This was explained by the formation of a bridge state, formed after population by the LUMO with one electron. Such a molecular orbital can facilitate charge transfer.

As this was an extended abstract with figures, it can not be viewed completely in this database. Introduction Bulk-heterojunction (BHJ) solar cells are composed of a nanoscale co-continuous composite of donor and acceptor phases, facilitating exciton dissociation. A conjugated, light-excitable polymer is most often used as an electron donor, and fullerene derivatives are the most widespread type of electron acceptor due to their high electron affinity and ability to transport charge [1]. An important advantage of such a system is that it can be casted from solvent, facilitating processing. Post-production annealing of such polymer:fullerene bulk heterojunction solar cells is vitally important, not only for fine-tuning the morphology and thus increasing the efficiency, but also for retaining the desired morphology during long-term operation [2-3]. However, knowing the optimal conditions for annealing temperatures and times requires knowledge about thermal transition temperatures and annealing kinetics of the blend systems. Using advanced fast-scanning thermal analysis techniques, the formation of nuclei and growth of crystals during heating or cooling can be reduced or avoided, allowing for the study of the crystallization processed during annealing. In this study, non-isothermal and isothermal crystallization kinetics of the P3HT:PCBM (poly(3-hexyl thiophene: [6,6] -phenyl C61 - butyric acid methyl ester) were studied by Rapid Heating Cooling Calorimetry (RHC) [4] and Fast Scanning Differential Chip Calorimetry (FSDCC) [5]. Methodology P3HT (Merck, Mw=35 000 g mol-1, Mw/Mn = 1.8; regioregularity greater than 98.5%) is mixed with PCBM (Solenne) in a 1:1 ratio and dissolved in chlorobenzene (CB) at a concentration of about 1-2.5 wt %, stirring overnight at 50°C. The solutions were deposited by drop-casting on large glass plates in a glove box under a nitrogen atmosphere to form films with a thickness of 1 µm. After drying in nitrogen atmosphere at room temperature for 50 hours to remove the residual solvent, the remaining solid films were scratched off the glass substrates and collected as a powder for RHC and FSDCC measurements. RHC experiments were performed on a prototype instrument made available by TA Instruments equipped with a liquid nitrogen cooling and specifically designed for operation at high scanning rates. Sample masses in the order of 250 - 300 µg were used in aluminium RHC crucibles. This allows for heating and cooling rates in the order of 2000 K/min. FSDCC was performed on a prototype Fast-Scanning Differential Chip Calorimeter (Rostock Univeristy, Germany) using Xensor Integration XI39399 chips, with an active area of 100 µm by 100 µm, having two on-chip heaters and 6 thermopiles for accurate temperature measurements. The whole chip calorimeter is submerged in a liquid nitrogen vessel, providing effective fast cooling. The highest rates achieved so far with this setup are in the order of 106 Ks-1, for sensor chips with a heated area of about 10 µm by 10 µm. The rates used in this work are limited to 5000 K.s-1. For both devices thermal annealing from the melt and from the glass were simulated by a temperature program as illustrated in figure 1, were the thermal transitions seen during the heating runs after isothermal treatment were used for analysis. Figure 1: Temperature program used to simulate thermal annealing, both from the glass and from the melt. The heating runs after the isothermal segments were used for data analysis. Results & Discussion Controlled fast heating and cooling are imperative for an isothermal crystallization study of rapidly crystallising systems such as P3HT:PCBM.. The fast heating and cooling capacity of advanced fast-scanning thermal analysis techniques enables the reduction of nuclei formation and crystal growth during heating or cooling, by restricting the time available for the blend to crystallise by quickly passing through the crystallisation temperature window that extends from the melting temperature down to the glass transition temperature. The thermal annealing process in P3HT:PCBM blends was studied first by performing RHC isothermal annealing experiments at 110°C for a wide range of isothermal times. All measurements were performed with a heating rate of 500 K.min-1 and ballistic cooling. Ballistic cooling reaches more than 1500 K.min-1 at the beginning of the cooling, which drops down to 750 K.min-1 around 60 °C. Figure 2 shows the subsequent heating curves of the system for increasing annealing times. It is clear that the cold crystallization enthalpies are decreasing and melting enthalpies are increasing by longer annealing times. Besides, by longer annealing at the isothermal annealing temperature, the step in Tg is getting smaller since less amorphous fraction is remaining in the material, and the Tg shifts to higher temperatures. As discussed in previous work, the crystallization of P3HT (having a lower Tg) from the blend is enriching the fraction of PCBM (having a higher Tg) in the remaining amorphous phase, leading to a higher Tg in the subsequent heating. Of course, the Tg is further increased by the close presence of crystalline domains, as is the case for semi-crystalline homopolymers. Another important remark is the clear difference between isothermal crystallisation from the melt and from the glass (without or with cooling before annealing). The crystallization rate is clearly higher when annealing from the glass [6]. Figure 2: RHC heating cycles at 500 K.min-1 for a P3HT:PCBM 1:1 blend after isothermal annealing both from the melt (left) and from the glass (right). This difference between the two possible paths of thermal annealing can be explained by a significant difference between the two in the amount of crystal nuclei. This suggests that the rates available in RHC are not sufficient to avoid most of the nucleation. When similar tests are conducted using FSDCC, using heating and cooling rates of 5000 K.s-1, cold crystallization disappears (see figure 3). There is also no longer a significant difference between isothermal crystallization from the melt and from the glass. Based on these results, it can be concluded that nucleation is mostly avoided by using heating and cooling rates available in FSDCC, and the crystallinity seen results only from the isothermal treatment. This allows for a reliable investigation of the crystallization processes during isothermal annealing, both from the glass and from the melt. Figure 3: FSDCC heating cycles at 5000 K.s-1 for a P3HT:PCBM 1:1 blend after isothermal annealing, both from the melt (left) and from the glass (right). Conclusion The isothermal crystallisation at the annealing temperature of 110 °C was investigated for 1:1 P3HT:PCBM using the advanced fast-scanning thermal analysis techniques RHC and FSDCC. RHC allowed for an in depth study of the isothermal crystallisation of these systems, but does not avoid most of the nucleation, leading to a difference in isothermal crystallisation rates for annealing treatments from either the glass or the melt. This difference, as well as cold crystallisation, disappears when FSDCC is used, owing to the much higher rates of heating and cooling. Because of this it is now possible to obtain only information about the isothermal crystallisation, without unwanted effect of the preceding thermal treatment. References 1. Thompson B.C. and Frechet J.M.J., Angewandte Chemie-International Edition, 2008. 47(1): p. 58. 2. Erb T., Zhokhavets U., Gobsch G., Raleva S., Stuhn B., Schilinsky P., Waldauf C., and Brabec C.J., Advanced Functional Materials, 2005. 15(7): p. 1193. 3. Hoppe H. and Sariciftci N.S., Journal of Materials Chemistry, 2006. 16(1): p. 45. 4. Danley R.L., Caulfield P.A., and Aubuchon S.R., American Laboratory, 2008. 40(1): p. 9. 5. Minakov A.A., van Herwaarden A.W., Wien W., Wurm A., and Schick C., Thermochimica Acta, 2007. 461(1-2): p. 96. 6. Demir F., Van den Brande N., Van Mele B., Bertho S., Vanderzande D., Manca J., and Van Assche G., Journal of Thermal Analysis and Calorimetry, 2011. 105(3): p.845.

Organic photovoltaics (OPVs) can still only achieve efficiencies below those of conventional silicon photovoltaics. To date the highest OPV efficiencies have been found for so-called bulk-heterojunction (BHJ) solar cells, where the active layer is a bi-continuous composite of donor (a conjugated polymer) and acceptor (a small molecule) phases. As in conventional polymer blend systems, the morphology formed will strongly influence the material characteristics, and post-production annealing has been shown to increase device efficiencies. In this study, the active layer of BHJ devices is analysed using fast-scanning calorimetry techniques in order to investigate the transitions that play a role in stability and morphology development. In particular, Rapid Heat-Cool Calorimetry (RHC) [1], and fast scanning differential chip calorimetry (FSDCC) were used. FSDCC especially shows great potential for these systems due to the very high scanning rates and the ability to study thin layer samples, like in actual BHJ devices.

In order to improve the thermal stability of polymer:fullerene bulk heterojunction solar cells, a new polymer, poly[2-methoxy-5-(2'-phenylethoxy)-1,4-phenylene vinylene] (MPE-PPV), has been designed and synthesized, which shows an increased glass transition temperature (Tg) of 111 °C. The thermal characteristics and phase behavior of MPE-PPV:[6,6]-phenyl C61-butyric acid methyl ester ([60]PCBM) blends was investigated by means of modulated temperature differential scanning calorimetry and rapid heating-cooling calorimetry. The thermal stability of MPE-PPV:[60]PCBM solar cells was compared with devices based on the reference MDMO-PPV material with a Tg of 45 °C. Monitoring of the photocurrent-voltage characteristics at elevated temperatures revealed that the use of high Tg MPE-PPV resulted in a substantial improvement of the thermal stability of the solar cells. Furthermore, a systematic transmission electron microscope study of the active polymer:fullerene layer at elevated temperatures likewise demonstrated a more stable morphology for the MPE-PPV:[60]PCBM blend. Both observations indicate that the use of high Tg MPE-PPV as donor material leads to a reduced free movement of the fullerene molecules within the active layer of the photovoltaic device. Finally, optimization of the PPV:fullerene solar cells revealed that for both types of devices the use of [6,6]-phenyl C71-butyric acid methyl ester ([70]PCBM) resulted in a substantial increase of current density and power conversion efficiency, up to 3.0% for MDMO-PPV:[70]PCBM and 2.3% for MPE-PPV:[70]PCBM.

When state-of-the-art bulk heterojunction (BHJ) solar cells with 'ideal' morphology are submitted to a prolonged storage/operation at elevated temperatures, a temperature induced disruption of the active layer morphology and photovoltaic degradation can occur. These detrimental effects of temperature are investigated with a variety of analytical and electro-optical techniques. An accelerated ageing system is used to study in-situ the degradation kinetics of the BHJ solar cells at various temperatures in order to obtain an accelerated ageing model to predict lifetime. Towards the long term use of organic solar cells in real life conditions, it is therefore demonstrated and highlighted that one of the challenges is the development of bulk heterojunction solar cells with stable morphology.

Phase separation and remixing are important transformations in the processing and application of polymer blends and polymer solutions. Modulated temperature DSC (MTDSC) proves to be very valuable for studying phase separation and remixing, for determining whether the systems are homogeneous or heterogeneous (from the glass transition(s)), to get an idea of the phase compositions, and for building phase or state diagrams and determining demixing or remixing kinetics. The origin of the contribution of the demixing-remixing phenomena to the MTDSC heat capacity signal will be discussed. For studying the thermoresponsive behavior of 100-nm thin films of polymer blends, AC chip calorimetry was successfully explored. It permits studying the influence of the substrate surface chemistry and the film thickness on the state diagram and the process kinetics. Combining these modern thermal analysis techniques, giving information on bulk and thin film thermal behavior, with hot-stage atomic force microscopy and nano-thermal analysis, provides a detailed insight in the material behavior. The paper will give some highlights of our recent work in these fields.

For the efficiency of bulk heterojunction solar cells based on blends of conjugated polymers and fullerenes, the formation of nanostructured morphology is crucial. As the diffusion distance of the excitons, the hole-electron pairs generated upon photon absorption is limited to a few nanometer, at least one of the phase dimensions should not exceed 10 nm. To permit an efficient charge transport of the charges generated, a co-continuous phase morphology is needed. A thorough study of the thermal transitions and isothermal annealing of polymer:fullerene blends revealed several key aspects for the usage of these materials for solar cell applications. The glass transition of the polymer:fullerene blends is crucial for the long-term stability of the required nanostructured morphology needed for optimal performance. The temperature dependence of the crystallization rate can be used to control the thermal annealing on the one hand, but might also prove useful for predicting the long-term stability at applicationtemperature from accelerated ageing tests at more elevated temperatures.

Thermosets, irreversibly cross-linked polymer networks having superior mechanical properties and increased thermal and chemical resistance, are often used in composites and coating applications. For coatings, concerns about the environmental safety of chromium-based corrosion inhibitors and the current lack of equally efficient replacements, increased the interest in alternative, sustainable and durable coating systems. Incorporating reversible covalent bonds in the polymer network structure builds in self-healing capacity through the reversible character of the polymer network, while still retaining mechanical properties comparable to conventional thermoset systems. The reversible character of the network enhances the processability of the polymer network materials, and introduces repairability and ultimately recyclability of the network polymer. Thermally-induced self-healing is a property of interest for coating applications. A reversible thermoset coating can be applied to a metal substrate to protect it from corrosion through its barrier properties and by healing sustained damage. As the healing relies on the thermally reversible reaction, the chemical potential for healing is in principle inexhaustible.

Introduction The last two decades a lot of research was spent on nanocomposite. The key factor in attaining the superior properties of these novel hybrid materials is the achievement of high levels of nanofiller dispersion of the incorporated low amounts of nanosized filler particles, resulting in a vast amount of polymer/filler interphase. [1] Materials and Methods The nanocomposites used in this work were prepared by melt mixing techniques, using Poly(?-caprolactone) (PCL) or Poly(propylene) (PP) as polymer matrix. As nanofiller particles we used silicates based on natural montmorillonite (exchanged with quaternary alkyl ammonium ions), multi walled carbon nanotubes (MWNTs) and cellulose nanocrystals. The nanocomposites of this work were prepared by melt mixing Morphological information was obtained from atomic force microscopy (AFM), Transmission electron microscopy (TEM) and Wide-angle X-ray scattering (WAXS). Small angle oscillatory shear rheometry ('dynamic rheometry') experiments werecarried out using a cone-and-plate geometry. Thermal characterization was performed using Modulated Temperature Differential Scanning Calorimetry (MTDSC). The mechanical properties of the various materials were assessed by determining their secant modulus (3-point bending mode). A simulation program called Macropac (Version 6.1) (Intelligensys Ltd) was used to model the packing of objects into a simulation container. Results and discussion A comprehensive overview of available methods for assessing nanofiller dispersion is presented for a wide range of layered silicate-based nanocomposites, carbon nanotube-based nanocomposites and nanocomposites containing cellulose nanocrystals. [2] Focusing on their respective strengths and weaknesses, rheological, mechanical and thermal characterization approaches are evaluated in direct relation to morphological information. [3] An advanced thermal analysis methodology (using MTDSC) is employed for the characterization of the PCL and PP nanocomposites. During quasi-isothermal crystallization, the presence of high aspect ratio nanofillers strongly affects the amount of crystalline-amorphous interface, thus increasing the recorded excess heat capacity (Cpexcess). This increase is in direct relation to the nanofiller dispersion quality. [4] In a second part of the work, the minimum loading of nanofiller particles needed to obtain a physical network (percolation network) was studied using a simulation program called Macropac (Intelligensys Ltd) (see Figure 1). [5] Figure 1: 3-D visualization of a packing of plate-like structures, mimicking silicate platelets, obtained using Macropac simulation software. Conclusions It is observed that the degree of filler dispersion is strongly influenced by the specific matrix/filler interactions and the processing conditions. It is concluded that each techniques used to study the nanofiller dispersion in nanocomposites provides information on a different level of the quality of the dispersion. In other words, a combination of different techniques is needed to make a qualitative assessment of the nanofiller dispersion. References [1] M. Alexandre, P. Dubois, Materials Science and Engineering. (2000), 28, 1-63. [2] Y. Habibi, A.-L. Goffin, et al. Journal of Materials Chemistry (2008), 18, 5002-5010. [3]H.E. Miltner, N. Watzeels, et al., European Polymer Journal (2010), 46, 984-996. [4] H.E. Miltner, N. Watzeels, et al., Journal of Materials Chemistry (2010), 20, 9531-9542. [5] Shiho Akagawa, Takashi Odagaki, Physical Review E (2007), 76, 051402(5).

In this work the phase behavior of [6,6]-phenyl C61-butyric acid methyl ester (PCBM) blends with different poly(phenylene vinylene) (PPV) samples is investigated by means of standard and modulated temperature differential scanning calorimetry (DSC and MTDSC) and rapid heat-cool calorimetry (RHC). The PPV conjugated polymers include poly(2-methoxy-5-(3?,7?-dimethyloctyloxy)-1,4-phenylene vinylene) (MDMO-PPV), High Tg-PPV which is a copolymer, and poly((2-methoxy-5-phenethoxy)-1,4-phenylene vinylene) (MPE-PPV). Comparisons of these PPV:PCBM blends with regioregular poly(3-hexyl thiophene) (P3HT):PCBM blends are made to see the different component miscibilities among different blends. The occurrence of liquid-liquid phase separation in the molten state of MDMO-PPV:PCBM and High Tg-PPV:PCBM blends is indicated by the coexistence of double glass transitions for blends with a PCBM weight fraction of around 80 wt%. This is in contrast to the P3HT:PCBM blends where no phase separation is observed. Due to its high cooling rate (about 2000 K min?1), RHC proves to be a useful tool to investigate the phase separation in PPV:PCBM blends through the glass transition of these crystallizable blends. P3HT is found to have much higher thermal stability than the PPV samples.

The last two decades a lot of research was spent on nanocomposite. The key factor in attaining the superior properties of these novel hybrid materials is the achievement of high levels of nanofiller dispersion of the incorporated low amounts of nanosized filler particles, resulting in a vast amount of polymer/filler interphase. [1] The Poly(?-caprolactone) (PCL) nanocomposites used in this work were prepared by melt mixing techniques. Getting the nanoparticles well-dispersed in order to exploit the high specific surface of the filler is a prerequisite for achieving significant property enhancement. An advanced thermal analysis methodology (Modulated Thermal Differential Scanning Calorimetry, MTDSC) is employed for the characterization of the PCL nanocomposites. During quasi-isothermal crystallization, the presence of high aspect ratio nanofillers strongly affects the amount of crystalline-amorphous interface, thus increasing the recorded excess heat capacity (Cpexcess). This increase is in direct relation to the nanofiller dispersion quality. [2] The interphase formation in nanocomposites around the nanofiller particles can also be studied using Dynamic Mechanical Analysis (DMA). Looking to e.g. the loss modulus, which represents the viscous behavior of our materials, we clearly observe a different behavior between the glass transition temperature (Tg) and the melting temperature (Tm) when comparing the pristine polymer with our nanocomposite samples. The latter is caused by the formation of a high polymer/filler interphase producing a vast amount of rigid amorphous interphase. A correlation between the change in mechanical properties in terms of e.g. the loss modulus and the quality of the level of dispersion of the nanofiller particles was observed, making DMA an interesting technique to study the dispersion quality of nanocomposites.

Transformations in polymers, such as polymerisation, melting/crystallization, and phase separation/remixing, are associated with changes in both rheological and thermal properties. Moreover, the influence of flow on these transformations and the occurrence of flow-induced transitions are important in the processing of polymer-based materials. For instance, it is known that the crystallization of polymers during the solidification step after processing strongly depends on the thermomechanical history of the material In this paper, new developments on the construction and evaluation of a RheoDSC, a hybrid measuring method that allows for a combined measurement of rheological and calorimetric properties, will be discussed. Combining MTDSC and rheometry in a single instrument will facilitate a simultaneous observation of the thermal and chemo-rheological changes in the material. Such an approach will allow the investigation of chemo-rheological changes during polymerization, of flow-induced transitions, of theinfluence of flow conditions on transformations in polymeric systems, and of polymer dynamics in general. The design, supported by modelling, the validation, and applications of the technique will be discussed.

We provide the first experimental evidence for the existence of a low concentration narrow UCST miscibility gap, which is the second of two narrow miscibility gaps constituting together adjacent UCST phase behavior. The existence of adjacent UCST miscibility phase behavior in aqueous polymer solutions has been theoretically predicted, but so far escaped experimental verification. We have been able to determine the low concentration narrow UCST miscibility gaps from the changes in apparent heat capacity observed in stepwise isothermal cooling modulated temperature differential scanning calorimetry (MTDSC) experiments. In wide-angle X-ray diffraction (WAXD) experiments it was unambiguously demonstrated that the MTDSC heat capacity changes are not due to crystallization. Together with earlier experimental results on the high concentration narrow UCST miscibility gap, the bimodal LCST miscibility gap and the sigmoidal melting line of ice the experimental results reported in this work complete the full experimental verification of the predicted complex phase behavior of aqueous solutions of PVME. As far as the authors are aware, this is the first system where adjacent UCST phase behavior is found. On the basis of the theoretical predictions the observed phase behavior could be more general and other systems may exist where similar behavior can be observed.

Thermosets are irreversibly cross-linked polymer networks which have superior mechanical properties and increased thermal and chemical resistance in comparison to their linear, un-cross-linked analogues. However, these thermosets exhibit severe limitations such as restricted process-ability and certainly repair-ability. To overcome these drawbacks, the incorporation of reversible cross-linking functionalities in the polymer backbone, such as Diels-Alder (DA) adducts, has been explored. This built-in reversibility allows the material to behave analogous to melting, molding and dissolution. The objective of this work is to asses the self-healing behaviour of a thermally reversible polymeric network for coating applications based on the Diels-Alder reaction (see figure below). The DA reaction is attractive as a reversible linkage as the retro-DA reaction occurs at moderate temperatures around 100 °C [1]. It is demonstrated that the network properties can be tailor-made by choosing the appropriate buildingblocks. In a first step, the furan functional compound is synthesized by an epoxy-amine reaction between furfuryl glycidyl ether (FGE) and a Jeffamine. The used Jeffamine series has a variable molar mass, resulting in different cross-linking densities in the final reversible network. Afterwards, the furan functional compound is mixed with a bismaleimide (BMI) in a 1:2 molar ratio and dissolved in chloroform. The epoxy-amine and Diels-Alder reactions were studied by micro-calorimetry and FTIR. Bulk properties were assessed after removal of the solvent. The thermal transitions of the bulk material were studied by MTDSC. The thermal stability of the reversible thermosets was evaluated by TGA. The flow behaviour of the bulk material was studied by means of rheological experiments at different temperatures. The reversible network coatings were applied on aluminum substrates by spincoating. Coating thicknesses were determined by local thermal analysis (LTA). The self-healing properties of the reversible thermoset coatings were evaluated by nanolithography and atomic force microscopy (AFM). References [1] A. Gandini, D. Coelho, A. Silvestre, European Polym. J. 44 (2008) 4029-4036.

The use of AC chip nanocalorimetry for studying the phase separation and remixing processes in thin (10-1000 nm) films of polymer blends is discussed.

The development of the RheoDSC instrument through heat transfer modelling using the finite element approach is discussed.

During the processing of polymers, the material is often exposed to heating and cooling rates considerably higher than the rates usually used in conventional DSC equipment. With project RHC [1], TA Instruments made an attempt to extend the range of heating and cooling rates conventional DSC systems can reach. In this presentation, the calibration of this fast-scanning DSC will be discussed. The prototype RHC used in our work can reach heating and cooling rates of 2000 K/min and 1500 K/min, respectively. To reach these high rates while retaining an operation similar as in a conventional DSC, the instrument was roughly scaled down by a tenfold. The RHC cell is of the Tzero(TM) type and is heated through infrared radiation and cooled with a liquid nitrogen cooling system. As thermal lag effects can be important at high heating rates of for larger sample masses, the thermal lag calibration procedure for the RHC will be discussed. The reproducibility of measurements of the melting temperature and enthalpy was studied. Through an investigation of the effects of sample mass and heating rate on the transformation temperatures and enthalpy, the need for a calibration depending on heating rate and sample mass was investigated [2]. The need for a different calibration in cooling was investigated by studying the symmetry of the thermal lag of transitions in three liquid crystalline materials in cooling and heating. Three transitions that behave symmetrically in heating and cooling could be identified, the RHC is behaving symmetrically in heating and cooling, and the same model can be used for describing the thermal lag in both heating and cooling. Next to the thermal lag, the enthalpy calibration was evaluated for a wide range of sample masses and heating rates. In addition, the enthalpy calibration was checked over the full temperature scale by measuring the heat capacity of sapphire and polymer reference materials. [1] R.L. Danley, P.A. Caulfield and S.R. Aubuchon, Am. Lab. , January (2008) 9-11 [2] G. Vanden Poel, A. Sargsyan, V. Mathot, Protocol proposed to the Research and Standardization group on "Temperature Calibration of Fast-Scanning Calorimeters", during the Technical Seminar of NaPolyNet, an FP7 program, see www.napolynet.eu (DIN, Berlin, Oct. 20, 2009).

In this study, the isothermal crystallization kinetics of poly(3-hexyl thiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) blend of a 50 wt% PCBM (1:1) were investigated by means of Rapid Heating Cooling Calorimetry (RHC). P3HT:PCBM blends are the state-of-the-art material for organic solar cells based on the bulk heterojunction concept. Their phase diagram was recently determined.1 Attaining the best performance requires a finely dispersed phase morphology, with crystalline P3HT and PCBM structures of 10-nm dimensions. During the production of the solar cells, the solvent-cast P3HT:PCBM blend is annealed at temperatures of typically 100°C to 140°C to create the desired phase morphology and increase the solar cell efficiency. However, if the annealing is too long, the efficiency again deteriorates again as a result of the formation of µm-sized PCBM needles. Recent research showed that the rate of efficiency loss shows a maximum around 125°C. As the annealing and the deterioration of the long-term stability both involve crystallization, the isothermal crystallization process of a P3HT:PCBM 1:1 blend was investigated by RHC. RHC, recently developed by TA Instruments, is a fast-scanning DSC designed for operation at scanning rates of up to 2000°C/min.2 It presents great benefits for the investigation of fast time-dependent transitions such as fast isothermal crystallization. Using the high cooling rates, crystallization during cooling can be avoided in certain cases, resulting in a glassy blend. Hence, it becomes possible to crystallize isothermally at temperatures closer to the glass transition Tg. The crystallization rate was obtained by fitting an Avrami kinetics model onto the evolution of the relative crystallinity versus time measured with RHC. Plotting the rate versus crystallization temperature (Tc) reached from the melt state gives a bimodal bell-shaped curve with maxima at 70°C and 110°C. Crystallization from the glassy state also exhibits a bimodal bell-shaped curve with two maxima, at 80°C and 125°C, and overall a higher crystallization rate (Figure 1). Similar observations were made for homopolymers. 3 Figure 1. Isothermal crystallization of a P3HT:PCBM 1:1 blend. References 1) Zhao J., Swinnen A., Van Assche G., Manca J., Vanderzande D. & B. Van Mele (2009) Journal of Physical Chemistry B, 113(6) 1587-1591. 2) Danley, R. L., P. A. Caulfield & S. R. Aubuchon (2008) American Laboratory, 40, 9-11. 3) Supaphol, P. & J.E. Spruiell (2001) Polymer, 42, 699-712

The demixing and remixing kinetics of aqueous solutions of poly(2-isopropyl-2-oxazoline) (PIPOZ) with four different chain lengths (number-average molar mass of 3300-13000 g mol(-1)) is studied by means of modulated temperature differential scanning calorimetry (MTDSC) in both nonisothermal and quasi-isothermal modes. The nonisothermal measurements show that the aqueous solutions of all four PIPOZ samples follow the lower critical solution temperature (LCST) phase behavior. Both the LCST and the corresponding polymer weight fraction (f(w)) decrease with increasing molar mass: 33.8 +/- 0.1 degrees C at 29.8 wt %, for 3300 g mol(-1) shifts to 26.2 +/- 0.1 degrees C at 19.8 wt % for 13000 g mol(-1). This typical type I phase behavior of aqueous solutions of PIPOZ is in contrast to the typical type II phase behavior of poly(N-isopropylacrylamide) (PNIPAM) which has isomeric repeat units. The demixing and remixing kinetics throughout the phase transition is studied by quasi-isothermal heat capacity measurements. Overall, the response for PIPOZ solutions is markedly faster than for PNIPAM solutions.

The present work aims at investigating the thermal properties of a wide range of semi-crystalline nanocomposites based on poly(amide)-6 (PA6), ethylene-vinyl acetate copolymer (EVA), poly(e-caprolactone) (PCL) or polypropylene (iPP), in combination with various types of nanofillers (layered silicates, carbon nanotubes, sepiolite, or POSS). We report on the effect of nanofillers on the quasi-isothermal crystallization behavior of the matrix as assessed from MTDSC experiments, evidencing profound changes in the matrix/filler interphase region. Depending on the system, the results are interpreted in terms of polymer/filler interaction, reduced chain segment mobility and altered crystalline morphology, supported by data from a wide range of complementary techniques.

The phase transitions in aqueous solutions of poly(N-isopropylacrylamide) (PNIPAM) brushes, covalently bound to the surface of gold nanoparticles, is studied by means of modulated temperature differential scanning calorimetry (MTDSC) in both non-isothermal and quasi-isothermal modes. The non-isothermal measurements show double demixing peaks in both the heat flow and the heat capacity traces for the solutions with a weight fraction (fw) below 50 wt%. Double remixing peaks are found for fw below 15 wt%.

The phase transition in aqueous solutions of semi-hydrophobically modified telechelic poly(2-isopropyl-2-oxazoline) (PIPOZ) with one octadecyl and one hydroxy end group (C18-PIPOZ-OH) is studied by means of modulated temperature differential scanning calorimetry (MTDSC) in both non-isothermal and quasi-isothermal modes.