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International audience; Here we report on reorganization on heating of a perspective organic semiconductor poly(3-(2′-ethyl)hexylthiophene) (P3EHT). P3EHT is an analogue of a well-known poly(3hexylthiophene) (P3HT), which has comparable optoelectronic properties and the advantage of a lower processing temperature. The processes of structural reorganization during heating of P3EHT have been explored with a combination of synchrotron X-ray scattering and ultrafast chip calorimetry. The signature of reorganization has been identified from an increase of d-spacing of 100 peak of the P3EHT unit cell. It was observed that reorganization operates during heating of P3EHT at conventional rates of a DSC experiment (i.e., at 10 deg/min), whereas it is largely suppressed at a heating rate of 100 deg/s. Despite the absence of reorganization at high heating rates the calorimetric curves exhibit pronounced double melting, which corroborates the model of the negative pressure building up during crystallization of semi-rigid chain polymers.

Homogeneous crystal nucleation in polyamide 66 (PA 66) was studied by a combination of atomic-force microscopy (AFM) and fast-scanning chip calorimetry (FSC), with a specific experimental setup all...

Kinetic methods have been widely used in analytical chemistry, generally using spectrophotometric or electrochemical detector. However, although enthalpimetric methods have been scarcely used, they may offer some interesting performances, like to be blind to the color and/or turbidity of the samples. This paper will be related with the description of some enthalpimetric kinetic methods and their instrumentation that could be used in these techniques, making a review on direct injection catalytic enthalpimetry, thermometric titration with catalytic endpoint detection, catalytic enthalpimetric flow injection analysis, continuous flow enthalpimetries, chip calorimetry, and trends of kinetic thermometric detection.

The effect of molar mass on the reorganization behavior of α′-crystals of poly ( l -lactic acid) (PLLA) has been investigated by fast scanning chip calorimetry. The α′-crystals of PLLA were formed by isothermal crystallization of the relaxed melt at 90 °C or lower temperatures, and were then heated at different rates between 2 and 200 K s − 1 . Slow heating permits for all PLLA samples of different molar mass between 2 and 576 kDa reorganization of α′- into α-crystals. It was found that the α′/α-transition is suppressed if heating occurs faster than 10 K s − 1 in case of the sample with a molar mass of 576 kDa, while the critical heating rate to suppress the formation of α-crystals is increased to 30 and 100 K/s in PLLA with molar masses of around 100 kDa and 2 kDa, respectively. The faster kinetics of the α′/α-transition in case of shorter macromolecules may be explained by faster melting of smaller α′-crystals, faster growth of α-crystals from the non-isotropic melt containing remnants/self-seed from molten α′-crystals, and/or a higher number of such α′-crystal remnants/self-seed.

Ultra-fast chip calorimetry is a modern thermal analysis technique based on MEMS-type sensors, which allows performing quantitative measurements on samples of only a few nanograms. However, calorimetry alone is sometimes insufficient for in-depth analysis of complex phase transitions occurring during the experiment. Therefore, in-operando structural analysis was found to be helpful in deciphering the nature of the corresponding structural transitions. Here we report on design of accessories for in-operando synchrotron-based X-ray scattering experiments at low temperatures as well as under different atmospheres and humidities. The examples of applications in polymer physics include analysis of the double-melting behavior of poly(trimethylene terephthalate) and structure formation processes in isotactic polypropylene.

Melting of original crystals and their recrystallization during heating were successfully separated for isothermally crystallized poly(butylene terephthalate) (PBT). The corresponding kinetics was determined and quantitatively discussed for a wide range of heating rates (0.1–100,000 K s -1 ) using fast-scanning chip calorimetry (FSC) and differential scanning calorimetry (DSC). The double melting peaks observed on the FSC curves are assigned to the melting of original crystals (low-temperature peak) and recrystallized and/or reorganized crystals (high-temperature peak). Heating rate dependence of the degree of recrystallization has been evaluated and the kinetics was discussed on the basis of Ozawa's method. Compared with the melt-crystallization and cold-crystallization, recrystallization kinetics is the fastest process. This is because many crystal remnants, which do not transform into the isotropic melt, act as athermal nuclei, and accelerate recrystallization.

The efficiency of linear trans γ-quinacridone to nucleate formation of β-crystals in isotactic polypropylene (iPP) at rapid cooling conditions has been evaluated by a combination of fast scanning chip calorimetry (FSC) and microfocus wide-angle X-ray scattering (WAXS). For samples containing different amount of γ-quinacridone, FSC cooling experiments revealed information about a critical cooling rate above which the crystallization temperature decreases to below 105 °C, that is, to temperatures at which the growth rate of α-crystals is higher than that of β-crystals. Microfocus WAXS analysis was then applied to gain information about the competition of formation of β- and α-crystals in samples prepared at well-defined conditions of cooling at rates up to 1000 K/s in the FSC. For iPP containing 1 and 500 ppm γ-quinacridone, the crystallization temperature is lower than 105 °C on cooling faster about 10 and 70 K/s, respectively, which then on further increase of the cooling rate leads to a distinct reduction of the β-crystal fraction. The study may be considered as a first successful attempt to quantify and interpret β-crystal formation in iPP containing γ-quinacridone at processing-relevant cooling conditions in the shed of light of the different temperature-dependence of the growth rates of α- and β-crystals.

Fast scanning chip calorimetry in its non-adiabatic version allows for heating and cooling at rates up to 106 K s−1, covering all polymer processing relevant rates. Furthermore it allows for systematic studies of nucleation, crystallization, melting and reorganization for a large number of polymers. After an introduction, open problems and the need for further investigation of polymer crystallization are explained, followed by a brief description of the novel technique of fast scanning chip calorimetry and its capability to shed further light on fundamental details of the polymer-crystallization process. In the fourth part, specific examples of non-isothermal and isothermal crystallization studies are provided, including the discussion of the effect of nucleating agents. The possibility to investigate homogeneous nucleation and its kinetics is highlighted too. The fifth part focuses on the analysis of the melting kinetics and the determination of the zero-entropy-production melting temperature.

Aging of glassy isotactic polybutene-1 (iPB-1) below the glass transition temperature (Tg) leads to remarkable acceleration of the subsequent isothermal crystallization due to the promotion of crystal nuclei. The formation and development of crystal nuclei during aging below Tg and during heating to the crystallization temperature have been probed by fast scanning chip calorimetry. The size and stability of the crystal nuclei change with the aging time. A short aging below Tg can only induce nuclei with small sizes which can grow into bigger stable ones during the heating process above Tg if the heating rate is not high enough. With a prolonged aging time below Tg, bigger stable nuclei can also be developed, and its number increases till reaches a maximum value. These results suggest that noncooperative local motions rather than cooperative segmental motions in glassy iPB-1 are responsible for the formation of crystal nuclei during aging below Tg.

The recent advances in polymer crystallization analysis by calorimetry are reviewed in this chapter. Following an introduction about polymer crystallization, the main calorimetric techniques used to investigate polymer crystallization are presented and discussed. Special emphasis is given to differential scanning calorimetry, fast scanning chip calorimetry, and temperature-modulated differential scanning calorimetry, where the main advantages of each technique are presented, for both isothermal and nonisothermal crystallization analyses, together with recommendations for their correct use to gain reliable experimental data. The chapter is completed with a section on flow-induced crystallization and details of combined techniques, which describe the advantages of coupling calorimetry with X-ray diffraction analysis, or optical microscopy, for a thorough investigation of polymer crystallization.

A novel infrared (IR) thermo-spectroscopic imaging technique is applied to the simultaneous measurements of IR transmittance spectroscopic images and thermal emission images of heat and mass transfers of styrene monomer polymerization in microfluidics. The heat released is observed in the mixing layer between two laminar flows of styrene monomer and toluene containing an initiator for polymerization. The concentration of chemical species and the independently measured temperature distribution within the mixing layer are determined at the microscale. This is the first report, of such a non-invasive method, to determine both the chemical composition and temperature distribution in microfluidic chemical reactions.

A combination of fast scanning chip calorimetry and X-ray ptychography is explored to study the effects of thermal annealing on the active layer of bulk heterojunction organic photovoltaics. The well-known P3HT/PC 61 BM 1:1 system is investigated as a test case. By using a custom chip calorimetry setup, it is possible to give a thermal treatment at 127 °C (400 K) to P3HT/PC 61 BM 1:1 thin layers, using a heating and cooling rate of 30000 K s −1 , after which the resulting morphology is investigated with X-ray ptychography. Applying only heating and cooling, without isothermal annealing, yields a featureless morphology. This corresponds well with thermal data which indicate a mixed amorphous phase only. For increasing isothermal annealing times, a well-defined morphology appears with increasing domain size, corresponding to the formation of an endothermal melting trajectory. This melting trajectory is expected to consist of both eutectic melting and melting of coarsened crystals. In contrast to chip calorimetry results, large domain sizes are obtained for heating and cooling without isothermal annealing at a conventional rate of 20 K min −1 . This initial morphology then develops further with increased isothermal annealing. The combination of chip calorimetry and ptychography allows separating the effects of each single thermal step on morphology development.

Rapid scanning chip calorimetry is a very useful tool for studying the glass transition and the related enthalpy relaxation kinetics. In this chapter, we review the practical aspects of making fictive temperature and enthalpy recovery measurements, including for ultrathin samples. The cooling rate dependence of the glass transition is discussed, as well as the Tg depression for ultrathin polystyrene and polycarbonate samples. The advantages of the short instrument response time and high cooling rates can be particularly exploited for enthalpy recovery measurements, and these are discussed in detail.

Fast chip calorimetry (FSC) offers fascinating new opportunities for calorimetric analyses that are based on the unprecedentedly wide range of heating and cooling rates that are accessible for controlled experiments. Coupled with the high rates that are applicable, FSC offers also ideal conditions for nucleation kinetics analyses that are based on a statistical approach, since such analyses require data sets with a sufficiently high statistical significance. Thus, applying high rates and thus performing many measurements per given time allows achieving high accuracy for the determined nucleation kinetics parameters. Yet while the calibration procedure for conventional differential scanning calorimeters (DSC) is well known, new procedures need to be established for fast chip calorimetry, because the calibration behavior depends on the position of the sample on the measurement area. In addition to a detailed discussion of the calibration of FSC, the nucleation rates of the solidification transformation as obtained from FSC measurements are discussed for two case examples that display the opportunities offered and the issues encountered in FSC-based nucleation kinetics analyses.

Thanks to the development of fast-scanning (chip-based) calorimeters (FSC) it is nowadays possible to achieve very high cooling rates, which enabled the study of polymer crystallization at large supercoolings, in conditions similar to what is experienced in real industrial processes. In such extreme conditions formation of structures very different from those commonly obtained under relatively slow cooling can occur.