Polyol

In organic chemistry, a polyol is an organic compound containing multiple hydroxyl groups (). The term "polyol" can have slightly different meanings depending on whether it is used in food science or polymer chemistry. Polyols containing two, three and four hydroxyl groups are diols, triols, and tetrols, respectively. Classification Polyols may be classified according to their chemistry. Some of these chemistries are polyether, polyester, polycarbonate and also acrylic polyols. Polyether polyols may be further subdivided and classified as polyethylene oxide or polyethylene glycol (PEG), polypropylene glycol (PPG) and Polytetrahydrofuran or PTMEG. These have 2, 3 and 4 carbons respectively per oxygen atom in the repeat unit. Polycaprolactone polyols are also commercially available. There is also an increasing trend to use biobased (and hence renewable) polyols. Uses Polyether polyols have numerous uses. As an example, polyurethane foam is a big user of polyether

Stitched shape memory alloy wires enhance damage recovery in self-healing fibre-reinforced polymer composites

Amaël Maximilien Cohades, Nathan Klaus Hostettler, Véronique Michaud

A major issue in composite technology is matrix micro-cracking due to low-velocity impact damage, which may severely limit service lifetimes of composite parts. In a novel approach, remarkable levels of healing of impact damage are obtained using shape memory alloy (SMA) wires to close longitudinal cracks in woven glass fibre-reinforced polymer plates with an epoxy-polycaprolactone (EP-PCL) matrix that shows dual-phase continuity. Thermal actuation of SMA wires stitched through the thickness of the stacked glass fibre plies introduces compressive loads to the cracks thanks to anchoring of the SMA loops at the fabric surfaces and debonding of the intervening threads, which prevents local deformation of the SMA, so that crack closure by about 200 μm is achievable. Concomitant expansion of the vascular network formed by the molten PCL fills the compressed cracks, resulting in highly effective healing on cooling, as demonstrated by C-scan images. Specimens stitched with SMA wires hence show almost complete healing, i.e. damage area recovery of 85%, after low-velocity impact at up to 17 J followed by heat treatment at 150 °C. This represents a 55% improvement over previous results for unstitched EP-PCL composites, and hence significantly greater degrees of healing than so far reported for this range of impact energies and this type of system.

2018

New efficient synthetic routes toward functionalised polyketides

Gérald Coste

RNA plays key roles in essential biological processes, such as protein synthesis, transcriptional regulation, splicing and retroviral replication. The structural diversity of RNA molecules and the lack of known RNA repair mechanisms make these biopolymers a challenging, yet very important target for therapeutic intervention. In particular, the increasing problems of bacterial resistance to antibiotics make the search for novel RNA binders of crucial importance. Among known RNA binders, aminoglycosides were among the first to be recognized as effectors of RNA functions. Despite the established bactericidal properties of aminoglycoside antibiotics, their therapeutic use is limited, as internal administration of aminoglycoside antibiotics at high doses results in clinical side effects. The 1,3-hydroxylamine motifs and deoxystreptamine moiety, present in all aminoglycosides, are the elements of recognition of RNA. Binding properties of these compounds is believed to be a three-dimensional electrostatic complementarity rather than highly specific contacts between the aminoglycosides and an RNA receptor site. Macrolides are a second class of compounds that bind to the ribosome. A large variety of natural compounds displaying various biological activities are recorded through literature. Most of them, share a macrocyclic lactone ring. Macrolides and aminoglycosides, despite their high potency, remain structurally highly sophisticated. The exploration of new pathways toward molecules of lower structural complexity was performed. Starting from a non iterative method for the synthesis of 15 carbon polyolic chains, (2R,4S)-1,5-bis[(2RS,4SR)-6-(benzyloxy)methoxy]tetrahydro-2H-pyran-2-yl]pentane-2,4-diol, a new intermediate, was isolated and selectively functionalised. In addition, efficient tools for the selective protection of hydroxyl moieties on polyol chains were developed allowing the synthesis of a library of structurally diverse 1,3-hydroxylamine and deoxystreptamine containing compounds. Deoxystreptamine dimers were found to be better RNA binders than 2-deoxystreptamine itself, while linear aminopolyols were found to be good linker candidates for the synthesis of deoxystreptamine dimers. Dynamic combinatorial libraries with a bacterial RNA fragment as biological target were implemented for the identification of new potent RNA binders. Based on macrolactonisation reaction or ring closing metathesis, efficient synthetic routes were explored for the synthesis of polyhydroxylated macrolactones requiring the isolation of few synthetic intermediate and limited protecting groups' manipulations. Glycolipids analogs were also produced on bis amides formation or ring closing metathesis for the synthesis of macrocyclic rings containing a bis(hemiacetal) scaffold and diamino or diamido linkers.

EPFL2007

New efficient synthetic routes toward functionalised polyketides

Gérald Coste

EPFL2007

Stitched shape memory alloy wires enhance damage recovery in self-healing fibre-reinforced polymer composites

New efficient synthetic routes toward functionalised polyketides

Catalytic conversion of N-Acetyl-D-Glucosamine (NAG) to small polyols and N-containing polyols

Stitched shape memory alloy wires enhance damage recovery in self-healing fibre-reinforced polymer composites

New efficient synthetic routes toward functionalised polyketides

Catalytic conversion of N-Acetyl-D-Glucosamine (NAG) to small polyols and N-containing polyols