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Polyesteramide (PEA) segmented copolymers represents an interesting class of thermoplastic elastomers (TPEs), containing of two different segments termed as hard segment (HS) and soft segment (SS). Chemically, SSs are polyether units having low T_g, which provides flexibility to the polymer chain, whereas HSs are short amide units, which can self-associate via hydrogen bonding and form a physical crosslinked network. The thermodynamic incompatibility between the SS and HS results in a two-phase morphology and sets the interesting properties of these copolymers. For example, they show the physical property of rubbers at room temperature, such as softness, flexibility and resilience, while at high temperature, the HS domains melt, making the segmented copolymers processable like thermoplastics. Thus, this temperature dependence of the HS domains allows the transition from a processable melt to a solid, rubber-like object, and vice versa. This last one can be tuned by playing with the chemical chain composition, type of the HSs (monodisperse or polydisperse) and the extent of phase separation, which strongly affects the copolymer properties and make them suitable for different applications in automotive, electric and consumer product industries. This thesis aims to synthesize well-defined amide-based PEAs of equal molar mass, but containing different HS concentrations (0, 5, 10, 15 and 20wt%) and to study their properties in order to understand in depth the role of HS density on morphology, thermal and viscoelastic properties. Parallel to this, it also aims to study the effect of polymer chain architecture, by synthesizing and studying PEAs with same HS density but with a dumbbell architecture. The structure-property relationship is established based on various experimental techniques like small-angle and wide-angle X-ray scattering, DSC, FTIR, FSC and shear rheology. The results show that the final properties of the samples like high-temperature stability, temperature, (FSA - Sciences de l'ingénieur) -- UCL, 2019

Fast scanning calorimetry has been applied in order to understand the phase transitions in thermoplastic elastomers (TPEs) based on well-defined multi-block copolymersmade of ‘soft’ polytetrahydrofuran and ‘hard’ terephthalate ester diamides. The intrinsically complex chemical structure of TPEs leads to complex phase transitions. By changing their thermal history over a wide range of temperature (from −100 ∘C to 200∘C) and cooling rates (from 10 to 4000 ∘C s−1), we clarify the origins of the various phases present in these materials. In particular, we study the different possibilities for the hard segments to associate depending on their mobility during the quenching phase, forming either strong and stable structures orweaker andmetastable ones. Besides, we demonstrate that a minimal cooling rate of 800 ∘C s−1 is necessary to keep these TPEs (made of short and monodisperse hard segments) amorphous leading to a subsequent cold crystallization when heating back, at around 30 ∘C. Finally,we validateour interpretationsby varying the copolymer composition (from10wt%to20wt%hardsegments), revealing the thermal invariance of poorly organized domains. Based on these data, we also discuss the importance of chain diffusion in the crystallization process. Applying fast scanning calorimetry allows us to link fundamental understanding to industrial application.

Thermoplastic elastomers (TPEs) based on segmented block-copolymers containing poly(- tetrahydrofuran) (pTHF) and terephthalate-based diamide groups (T4T) were synthesized via polycondensation. While pTHF is known to be flexible and amorphous at rest, the more rigid T4T crystallized in different ways depending on both chain composition and sample preparation conditions. Increasing the content of hard-segments (HS) from 5 to 20% in weight leads to a substantial increase of the melting point Tm by more than 60 C. We have systematically investigated the multiscale (1 Å - 50 nm) organization of the HSs (of fractions from 5% to 20%) by means of DSC, WAXS and (ultra) small angle X-ray scattering (U)SAXS. By increasing HS content, hence the rigidity of the chain, scattering experiments unambiguously show the formation of bigger and better defined ribbon-like crystallites, as well as the densification of the network they form.We propose a scenario for rationalizing the local T4T-HSs packing and the crystallites anisotropy at the mesoscale (1e10 nm) for HS fraction above 5%. Moreover, following in-situ the crystallization of TPEs with large HS fraction (20%), we highlight the presence of “persistent aggregates” present at T > Tm and study the ribbon-like crystallites growth mechanism during cooling from the melt state.