Three-dimensional self-assembled morphologies, whether synthesised by nature or by man, are typically modelled in terms of perfectly periodic lattices. In many cases, their function is defined by these periodic space groups, such as the colour response of photonic materials. However, close examination of these morphologies reveals deviations from perfection. Real 3D lattices, whether created by molecular self-assembly or surfactant systems, exhibit disorder at different length scales, from unit cell distortions to grain boundaries.

My talk will focus on these different levels of disorder, discussing their causes and consequences for the function that results from the order-disorder interplay. I will also explore ways to control the level of disorder that can be chosen in the fabrication of self-assembled lattices and discuss the advantages of these networks compared to perfectly ordered arrays.

We report the first reversible addition-fragmentation chain transfer polymerisation-induced self-assembly (RAFT-PISA) in ionic liquid (IL) that proceeds under emulsion conditions. Moreover, this formulation exploits refractive index contrast matching of the IL solvent and polymer to generate highly transparent nanoparticle dispersions, even when nanoparticle diameters exceeded 100 nm. Detailed analysis using small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) confirmed the presence of spherical nanoparticles. Furthermore, the synthesis of diblock copolymers via this new PISA formulation was directly compared to equivalent syntheses conducted in DMF or ethanol/water mixtures. It was found that syntheses conducted in IL resulted in the highest monomer conversions (up to >99%) and lowest dispersity values (as low as 1.16) in the shortest reaction times (2 hours) compared to the other solvent systems. This work demonstrates the use of ILs as a more sustainable and effective solvent for RAFT PISA via the development of the first emulsion PISA formulation in IL.

Elastomers have been an indispensable material in our daily life since the discovery of vulcanization by Goodyear in the mid-19th century. In the preparation of elastomers, random nature of crosslinking reaction often leads to various structural defects in the polymer network structure. Such defects deteriorate the performance of the material. Recently, more homogeneous network structure with less defects has been realized by the "module-assembly" strategy, in which the network is constructed by end-linking of monodisperse prepolymers[1]. Herein, we present our recent discovery of the unique mechanical properties of elastomers synthesized via the module-assembly strategy[2].
Figure 1 shows the synthetic scheme of the elastomer. 4-arm or 3-arm star poly(4-methyl-ε-caprolactone) (PMCL) was synthesized and end-linked via efficient click reaction, yielding a gel. A solvent-free elastomer was obtained by solvent removal. The elastomer showed not only a high tensile strength and stretchability (Figure 2). The high stretchability was found to be due to the contraction of network chains upon solvent removal from the gel, which has been known as supercoiling. More interestingly, there was the significant upturn in the stress starting at λ ~ 15, i.e., it showed a considerable strain stiffening. We found that the observed strain stiffening capability was beyond that of any other soft materials known to date. In situ X-ray scattering measurements under tension revealed that the strain-induced ordering of the network chains was mainly responsible for the extraordinary strain stiffening capability and tensile strength (Figure 3).

Blending one elastomer with another elastomer is a well-known strategy to improve some of its macroscopic properties. This is the case for immiscible Natural Rubber (NR) / poly(butadiene) (BR) blends, widely used in the tire industry, for which the BR component allows to enhance the NR wear resistance¹.

Nevertheless, the presence of the BR domains may simultaneously influence the cross-linking within the NR domains. In this context, investigating the cross-linking process occurring in each type of domains (NR-rich and BR-rich phases) is a key information to describe the elastic behaviour of the blends. Such an information could not be derived until now, since the approaches conventionally used for elastomers (swelling, DMA) cannot discard the contribution from both kinds of domains to the cross-link density of the blends.

In this work, a particular attention was paid to describe the distribution of the cross-linking density, selectively, in both kinds of blend domains², as shown in Figure 1. Solid-state NMR revealed that the cross-link density is more widely distributed within the BR-rich domains, with the presence of a higher proportion of short elastically-active chains within the BR phase³. Besides, the cross-link heterogeneities in both NR- and BR-domains were found to be independent of the BR content and thus, of the blend morphology, which was studied by AFM-IR. The combination of these new results was used to get a deeper understanding of their mechanical behaviour in the low-deformation range.

Thermostable polymer matrices are widely used in aerospace industry and microelectronics. Among them, thermosetting benzoxazines (BOAs) and cyanate ester resins (CERs) expand the high-temperature operation regime, thus constituting the most promising materials.
It is well known that the BOA ring is stable at low temperature, but a ring opening reaction occurs at high temperature, thus affording novolac type polybenzoxazines (PBZs) with both phenolic hydroxyl group and tertiary amine group. The resulting polymers are characterized by low volumetric shrinkage upon polymerization, low moisture absorption, excellent chemical resistance, flame retardancy, electrical properties, thermal stability, mechanical properties; and very rich molecular design flexibility [1]. On the other hand, CERs differ from other thermosets by a very regular structure of the resulting networks, namely polycyanurates (PCNs), obtained by their polycyclotrimerization. They have received much attention because of their unique combination of physical properties, including high thermal stability (> 400°C), high glass transition temperature (> 270°C), high fire-, radiation and chemical resistance, low water absorption, high adhesion to different substrates, and excellent dielectric properties (ε = 2.6−3.1) [2,3]. As a result, CERs are currently used as structural or functional materials in aeronautics, printed circuit boards or adhesives.
In the present work, we address the copolymerization kinetics of CERs and BOAs by FTIR and DSC in order to get an insight into the structure and properties of resulting hybrid thermosets based on PCNs and PBZs. Novel nanocomposites derived from such hybrid thermosets and various functionalized polyhedral oligomeric silsesquioxane (POSS) as reactive nanofillers are also developed.

This study presents the synthesis, characterization, and potential applications of a novel photoswitchable polysiloxane elastomer. The photoswitching functionality is introduced through the incorporation of arylazopyrazole (AAP) into the elastomer, which undergoes a reversible trans-cis isomerization upon exposure to UV light, returning to the trans form under green light or thermal conditions. AAP was covalently bonded to the polysiloxane backbone via esterification, resulting in a physically cross-linked polymer that can be processed into free-standing films through melt pressing.
The photoactive AAP units enable the polymer to alter its properties in response to light. Using an interdigitated electrode setup, we measured dielectric permittivity, loss tangent (tan(δ)), and conductivity while exposing the sample to light. These properties exhibit an increase upon light exposure and revert when the light is turned off. The observed changes are attributed to two simultaneous phenomena: heating the samples when exposed to light of any wavelength and trans-cis isomerization of the AAP molecules under UV light. To differentiate these effects, we studied temperature independent frequencies, revealing that the trans-cis isomerization causes a 70 % increase in dielectric permittivity.
This capability suggests potential applications in electronic devices that could reversibly modify their dielectric permittivity and capacitance when exposed to UV light.