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Phase behaviour of poly(N-vinyl caprolactam) in water

Abstract The solution behaviour of the system poly(N-vinyl caprolactam)/water has been studied. Experiments and theoretical calculations indicate a typical Flory–Huggins (Type I) demixing behaviour with a lower critical solution temperature (LCST). The critical concentration and LCST shift to lower values with increasing molar mass of the polymer. The phenomenological description of such a system predicts a continuous temperature controlled swelling behaviour of the corresponding network. A comparison with literature data confirms this prediction. A calorimetric study of the crystallisation and melting behaviour of water and the concentration dependence of the glass transition temperature, gives no evidence for the formation of a polymer/solvent complex.

Thiol–ene chemistry for polymer coatings and surface modification – building in sustainability and performance

Future advancement of coatings relies on new synthetic building blocks and methods that enable added functionality, while minimising the environmental impact and cost. This review highlights the use of thiol–ene chemistry for surface modification and coatings, a topic of increasing interest in academic and industrial context since the beginning of this century. This chemistry platform has the advantages of rapid and uniform cross-linking, delayed gelation, reduced shrinkage, and insensitivity to oxygen. Recently, it resulted in significant advances in UV-cured coatings, including pigmented acrylate coatings and waterborne polyurethane dispersions. Moreover, biobased coatings were developed via thiol–ene coupling of unsaturated moieties in vegetable oils with multifunctional thiols, resulting in tunable properties. The homogeneous thiol–ene network formation has also been employed in hybrid coatings, yielding synergistic effects of the inorganic components within the thiol–ene matrix. Moreover, the UV-triggered thiol–ene reaction is fast and efficient, which is useful for surface modification with spatial and temporal control. In general, this review will critically describe how thiol–ene chemistry became a powerful tool for the sustainable development of functional coating materials and surfaces with a variety of building blocks.

ADMET and TAD chemistry: a sustainable alliance

A versatile, additive-free post-polymerisation functionalisation method for acyclic diene metathesis (ADMET) derived polymers, utilising 1,2,4-triazoline-3,5-dione (TAD) chemistry, is reported. Several diene monomers have been synthesised starting from 10-undecenoic acid derivatives and subsequently polymerised via ADMET polymerisation reaction. Post-polymerisation functionalisation of the poly-unsaturated macromolecules with several substituted TAD compounds was shown to achieve full conversions within 6 hours. Also, the functionalised polymers could be chemically crosslinked with a bivalent triazolinedione crosslinker. The glass transition temperature of the resulting materials could be tuned by varying the degree of functionalisation, the polymer backbone, the TAD substituent and the crosslinking density.

Composition and self-irradiation effects on the positron annihilation lifetime properties of poly(ethylene-co-vinyl acetate).

Abstract The behavior of the copolymer poly(ethylene-co-vinyl acetate), with different amounts of vinyl acetate (VA) (2, 4.5, 9 and 19 w/w%, respectively), has been studied by performing positron lifetime measurements as a function of temperature. An overall reduction of the ortho-positronium formation probability I3 with increasing VA content is observed. The copolymers with 2, 4.5 and 9 w/w% VA show a V-shaped I3 evolution with temperature, caused by positron irradiation induced ionization, whereas the copolymer with 19 w/w% VA has become practically inert to self-irradiation effects.

SEGMENTED POLYMER NETWORKS BY CATIONIC POLYMERIZATION: DESIGN AND APPLICATIONS

Well-defined acrylate terminated bis-macromonomers of poly(vinylether)s, poly(2-alkyl-2-oxazoline)s and poly(1,3-dioxolane) have been synthesized by making use of macromolecular design concepts of cationic polymerization. The acrylate end groups of the bis-macromonomers have been radically copolymerized with vinyl monomers such as methyl methacrylate, butyl acrylate and hydroxyethyl acrylate for the synthesis of hydrophobic, amphiphilic or hydrophilic segmented copolymer networks. The nature and the ratio of the two components and the molecular weight of the bis-macromonomers determine the morphology, hydrophilic/hydrophobic balance and swelling properties of the network structures. These parameters will be described in terms of the use of these materials for a variety of purposes, such as for pervaporation, shape memory properties or damping applications.

Thermalisation of Positronium in Polymers

A new model is presented which describes the annihilation of positronium (Ps) in polymers. Ps is formed in the bulk and is trapped into the free volume holes with epithermal initial energy and it thermalises towards its ground state during its lifespan through elastic collisions with the inner walls, This thermalisation is characterised by an asymptotic Ps-decay constant lambda(po)(infinity), an energy ratio parameter xi and by a relaxation parameter, from which the free volume hole size R, the effective recoiling mass M, and the quenching probability per collision mu can be obtained, We have verified this model on a set of cross-linked PMMA samples.