Thermoreversibly crosslinked poly(ε-caprolactone) as recyclable shape-memory polymer network

in Macromolecular Rapid Communications (2011), 32(16), 1264-1269

A new concept to build shape memory polymers (SMP) combining outstanding fixity and recovery ratios (both above 99% after only one training cycle) typical of chemically crosslinked SMPs with ... [more ▼]

A new concept to build shape memory polymers (SMP) combining outstanding fixity and recovery ratios (both above 99% after only one training cycle) typical of chemically crosslinked SMPs with reprocessability restricted to physically crosslinked SMPs is demonstrated by covalently bonding, through thermoreversible Diels–Alder (DA) adducts, star-shaped poly(epsilon-caprolactones) (PCL) end-functionalized by furan and maleimide moieties. A PCL network is easily prepared by melt-blending complementary end-functional star polymers in retro DA regime, then by curing at lower temperature to favour the DA cycloaddition. Such covalent network can be reprocessed when heated again at the retro DA temperature. The resulting SMP shows still excellent shape memory properties attesting for its good recyclability. [less ▲]

Macromolecular engineering of biodegradable polyesters by ring-opening polymerization and 'Click' chemistry

in Macromolecular Rapid Communications (2008), 29(12-13), 982-997

Biodegradability makes aliphatic polyesters valuable candidates for biomaterials and environmentally friendly thermoplastics. Nevertheless, their chemical modification, which is mandatory for a series of ... [more ▼]

Biodegradability makes aliphatic polyesters valuable candidates for biomaterials and environmentally friendly thermoplastics. Nevertheless, their chemical modification, which is mandatory for a series of potential applications, is usually a problem because it must be carried out under very mild conditions in order to prevent degradation by hydrolysis and/or transesterification from occurring. In this review, the copper(i) -catalyzed azide-alkyne cycloaddition, which is a click reaction, is shown to be very efficient to bypass these problems and to tailor the macromolecular architecture and functionality of those polyesters without facing undesired degradation reactions. [less ▲]

Fast controlled radical polymerization of styrene mediated by oligomeric nitroxides formed in situ

in Macromolecular Rapid Communications (2007), 28(2), 147-151

In the presence of an oligomeric hindered secondary amine added with peracetic acid as the oxidant, radical polymerization of styrene is fast and controlled at 110 degrees C. Under these experimental ... [more ▼]

In the presence of an oligomeric hindered secondary amine added with peracetic acid as the oxidant, radical polymerization of styrene is fast and controlled at 110 degrees C. Under these experimental conditions, an oligomeric nitroxide is formed in situ. This polymerization is 2.5 faster than polymerization mediated by the alkoxyamine derivated from TIPNO (2,2,5-trimethyl-4- phenyl-3-azahexane-3-nitroxide), which generates a low molar mass nitroxide. Similarly, substitution of a low molar mass secondary amine, 2,2,6, 6-tetramethylpiperidone (4-oxo-TMP), for the oligomeric secondary amine maintains the control on the polymerization, which is however 4.6 times slower, all the other conditions being the same. The in situ formation of the oligomeric nitroxide has been confirmed by electron spin resonance (ESR). [less ▲]

Preparation of well-defined PVOH/C60 nanohybrids by cobalt-mediated radical polymerization of vinyl acetate

in Macromolecular Rapid Communications (2006), 27(7), 498-504

Poly(vinyl acetate) chains end-capped by a Co(acac)(2) complex [PVAc-Co(acac)(2)] were prepared by bulk cobalt-mediated radical polymerization (CMRP) of vinyl acetate and used for grafting fullerene (C60 ... [more ▼]

Poly(vinyl acetate) chains end-capped by a Co(acac)(2) complex [PVAc-Co(acac)(2)] were prepared by bulk cobalt-mediated radical polymerization (CMRP) of vinyl acetate and used for grafting fullerene (C60) with four PVAc arms at low temperature (30 degrees C). A photoactive water-soluble poly(vinyl alcohol)/C60 nanohybrid was then prepared by hydrolysis of the PVAc arms of the nanohybrid. Because of photoactivity and very low cytotoxicity, this type of water-soluble nanohybrid is very promising for the photodynamic cancer therapy. [less ▲]

Sequential electrografting and ring opening metathesis polymerization: a strategy for the tailoring of conductive surfaces

in Macromolecular Rapid Communications (2005), 26(10), 779-783

An electrografting technique has been combined with ring-opening metathesis polymerization (ROMP). Poly(allyl methacrylate) chains have been chemisorbed onto steel and carbon plates under an appropriate ... [more ▼]

An electrografting technique has been combined with ring-opening metathesis polymerization (ROMP). Poly(allyl methacrylate) chains have been chemisorbed onto steel and carbon plates under an appropriate cathodic potential in N,N-dimethylformamide. The allyl moieties have been converted into Ru catalysts active in ROMP of norbornene and its derivatives. Initiation of ROMP from the surface is an efficient strategy to prepare strongly adhering coatings of tunable thickness and hydrophilic/hydrophobic balance, depending on the norbornene derivative polymerized at the surface. [less ▲]

Functionalization of multi-walled carbon nanotubes by electrografting of polyacrylonitrile

in Macromolecular Rapid Communications (2004), 25(10), 987-990

As a result of their unique architecture and remarkable mechanical and electrical properties[1,2] carbon nanotubes (CNTs)[3] have great potential that remains, however, un-exploited because of poor ... [more ▼]

As a result of their unique architecture and remarkable mechanical and electrical properties[1,2] carbon nanotubes (CNTs)[3] have great potential that remains, however, un-exploited because of poor dispersibility in liquids and problems of processability, Major efforts have, therefore, been devoted towards any modification of the CNTs that could improve their handling[4,5] Typically, chemical modification of CNTs is based on severe oxidation processes that often damage the tubes[5] Mild and single-step electrochemical modification of CNTs is a valuable alternative to the oxidative treatment. There are several reports in the scientific literature on the electrochemical functionalization of CNTs by electroreduction of diazonium salts,[6-8] and on the halogenation of MWNTs by electrolysis However, the grafting of polymers instead of low-molecular-weight compounds onto CNTs by an electrochemical process is a possible strategy for dispersing CNTs in polymer matrices and improving the mechanical properties of CNT-based nanocomposites.. For the past few years, we have been interested in the electiografting of insulating polymer films onto cathodic surfaces, for example, nickel and glassy carbon, provided that the potential and solvent are properly selected.[10-15] These films are designated as "grafted films", because they have the unique property of remaining attached to the electrode surface even when they are prepared and kept in a solvent in which the polymer is highly soluble. The extension of this technique to CNTs has been explored with acrylonitrile as monomer. This communication aims at reporting the functionaliza-tion of multi-walled carbon nanotubes (MWNTs) by the electropolymerization of acrylonitrile. [less ▲]

Novel aliphatic polyesters based on functional cyclic (di)esters

in Macromolecular Rapid Communications (2003), 24(2), 161-172

Recent progress in the chemical synthesis of novel aliphatic polyesters via ring-opening polymerization of functional cyclic (di)esters are reviewed in this article. Syntheses of these functional ... [more ▼]

Recent progress in the chemical synthesis of novel aliphatic polyesters via ring-opening polymerization of functional cyclic (di)esters are reviewed in this article. Syntheses of these functional aliphatic polyesters are being classified into three groups according to the structure of the cyclic monomers: (i) cyclic diesters, (ii) morpholine-2,5-dione derivatives, and (iii) cyclic esters. Progress in the synthesis and polymerization of monomers in each category is reported with an emphasis on controlled synthesis. The recent achievements have enabled the synthesis of a variety of novel aliphatic polyesters, including hydrophilic, halogenated, and unsaturated polyesters. [less ▲]

Association of telechelic ionomers in apolar solvents

in Macromolecular Rapid Communications (2001), 22

The associative properties of well-defined halatotelechelic ionomers in an apolar solvent were studied by means of dynamic mechanical spectroscopy, small-angle X-ray scattering, as well as static and ... [more ▼]

The associative properties of well-defined halatotelechelic ionomers in an apolar solvent were studied by means of dynamic mechanical spectroscopy, small-angle X-ray scattering, as well as static and dynamic light scattering. The effect of end-functionalisation was investigated by comparing results on polystyrene (PS) and polyisoprene (PI) precursors using PS and PI of the same molar mass modified at one or both ends with sulfonate groups. The molar-mass dependence was investigated by comparing difunctionalised samples with different molar masses and the influence of the backbone by comparing polystyrene and polyisoprene. Experimental data suggest a relatively simple model for the association of this material. At low concentrations, the polymer chains organise themselves into well-defined reversed micelles, so-called flowers. Above a certain concentration C+, the flowers associate into larger aggregates according to an open association mechanism. At a critical concentration Cgel, the aggregates fill the whole space and a transient network is formed most likely by a percolation process. A semi-quantitative description of the associating process can be obtained by considering an open association mechanism properly combined with inter-particle interactions. [less ▲]

Reverse atom-transfer radical polymerization at room temperature

in Macromolecular Rapid Communications (2001), 22(6), 439-443

This paper aims at reporting on the living/controlled radical polymerization of methyl methacrylate initiated with the benzoyl peroxide (BPO)/CuIX (X=Br,Cl)/2,2'-bipyridine (bpy) redox system at room ... [more ▼]

This paper aims at reporting on the living/controlled radical polymerization of methyl methacrylate initiated with the benzoyl peroxide (BPO)/CuIX (X=Br,Cl)/2,2'-bipyridine (bpy) redox system at room temperature. No control is observed for the polymerization conducted in bulk and in toluene, whereas a polymer with predetermined molecular weight and rather narrow molecular weight distribution is formed in butanone. The solvent has thus a decisive effect on the reverse atom-transfer radical polymerization of methyl methacrylate initiated with the BPO/CuIX (X = Br,Cl)/bpy ternary system at 25°C. [less ▲]

First example of an unsymmetrical difunctional monomer polymerizable by two living/controlled methods

in Macromolecular Rapid Communications (2000), 21(11), 779-784

In this paper the synthesis and (co)polymerizations of 4-(acryloyloxy)-epsilon-caprolactone are reported. This new monomer can be polymerized in a living/controlled way by two different polymerization ... [more ▼]

In this paper the synthesis and (co)polymerizations of 4-(acryloyloxy)-epsilon-caprolactone are reported. This new monomer can be polymerized in a living/controlled way by two different polymerization mechanisms: atom transfer radical polymerization (ATRP) and ring-opening polymerization (ROP). ATRP, which was carried out at 90 degrees C using NiBr2(PPh3)(2), leads to new polyacrylates containing pendant caprolactone functionalities with controlled molecular weights and narrow polydispersities (M-w/M(p)similar to 1.1). Alternatively, ROP of this functional epsilon-caprolactone bearing a pendant acrylate functionality leads to new poly(4-(acryloyloxy) caprolactone) as well as random copolymers when epsilon-caprolactone and L,L-lactide are added as comonomers. The (co)polymerizations were carried out using either (Al((OPr)-Pr-i)(3) in toluene at 25 degrees C or Sn(Oct)(2) as a catalyst at 110 degrees C producing (co)polymers with controlled molecular weights and narrow polydispersities (M-w/M(n)similar to 1.2). As a potential application, the introduction of acrylate pendant groups into the polyesters facilitated the preparation of cross-linked biodegradable materials either thermally or by irradiation with ultraviolet light radical curing. [less ▲]