ABSTRACT
Porous materials were produced based on high internal phase emulsions (HIPE) formulation stabilized by modified cellulose nanocrystals (CNCs). CNCs were first modified with bromoisobutyryl bromide and used as Pickering emulsion stabilizers to formulate highly concentrated inverse emulsions. Solid foams with an open porosity were successively produced by free radical polymerization of styrene/divinylbenzene continuous phase. The final materials were characterized regarding their cell size distribution, porosity and mechanical properties and then compared with well-known styrene/DVB polyHIPE stabilized either with usual surfactants or solid particles.
ABSTRACT
In this contribution, the principle of spontaneous surface segregation has been applied for the preparation of polypeptide-functionalized polystyrene microspheres. For that purpose, an amphiphilic diblock copolymer was introduced in the mixture styrene/divinylbenzene and polymerized using AIBN as initiator. During the polymerization, cross-linked particles were obtained in which the diblock copolymer was encapsulated. The amphiphilic diblock copolymers used throughout this study contain a hydrophilic polypeptide segment, either poly(L-lysine) or poly(L-glutamic acid) and a hydrophobic polystyrene block. After 4 h of polymerization, rather monodisperse particles with sizes of approximately 3-4 microm were obtained. Upon annealing in hot water, the hydrophilic polypeptides migrate to the interface, hence, either positively charged or neutral particles were obtained when poly(L-lysine) is revealed at the surface and exposed to acidic or basic pH, respectively. On the opposite, negatively charged particles were achieved in basic pH water by using poly(L-glutamic acid) as additive. The surface chemical composition was modified by changing the environment of the particles. Thus, exposure in toluene provoked a surface rearrangement, and due to its affinity, the polystyrene block reorients toward the interface.
Subject(s)
Microspheres , Peptides/chemistry , Polymers/chemical synthesis , Polystyrenes/chemistry , Particle Size , Polyglutamic Acid , Polylysine , Surface PropertiesABSTRACT
Highly crosslinked functional polymer particles with narrow size distribution have been produced by precipitation copolymerization of divinylbenzene, ethylene glycol dimethacrylate and vinylbenzyl chloride using a simple reflux protocol. After establishing the satisfactory synthesis conditions, we produced uniform chlorobenzyl particles with different size depending on the polymerization times. The porosity of those particles was modulated from microporous to mesoporous structure by using various porogens such as toluene, dodecanol, cyclohexanol and polypropylene glycol. These particles were tested as stationary phase in high-performance liquid chromatography for the separation of polycyclic aromatic hydrocarbons in reversed-phase mode. The separation was observed even for elution 100% organic (methanol) without any participation of water fraction in the eluent composition. The influences of particles size, specific surface area and packing conditions on the separation behavior were investigated.
Subject(s)
Chlorobenzenes/chemistry , Chromatography, Liquid/methods , Microspheres , Polymers/chemical synthesis , Chemical Precipitation , Cross-Linking Reagents , Particle Size , Polymers/chemistry , Porosity , SolventsABSTRACT
Titanium alloys exhibit excellent biocompatibility and corrosion resistance in the body fluid and possess mechanical properties similar of the bones' properties. When the loss of osseous is important in osseous surgery, large biomaterials are implanted and should be accepted by the organism. For increasing the biomaterials biocompatibility, biological compounds can be linked or deposited on the material surface making them biologically active. In order to study the tissue-implant interaction and to favor osteoblast-adhesion onto titanium, our work deals with the grafting of cell-binding peptides containing the Arginine-Glycine-Aspartic acid (RGD) sequence. In the present study, we focus on the elaboration of patterned biomaterial surfaces with highly functionalized nanodomains. The strategy of RGD peptide immobilization involves first the grafting if an amino-functional organosilane (APTES). Then, each of the free amino moieties were used as an initiator core for a dendrimer-like synthesis to multiply the number of free groups available for RGD immobilization on the material surface.
Subject(s)
Coated Materials, Biocompatible/chemistry , Nanostructures/chemistry , Nanostructures/ultrastructure , Oligopeptides/chemistry , Titanium/chemistry , Adsorption , Bone Substitutes/chemistry , Crystallization/methods , Materials Testing , Particle Size , Protein Binding , Surface PropertiesABSTRACT
Using poly(omega-norbornenyl polystyrene) as a model we studied the conformation and the structure of branched polymer chains each of whose backbone constitutive units bear a branch. The parameters taken into account are: the polymerisation degree of the backbone, the molar mass of the branches and the solution concentration. The effect of the global conformation of these polymacromonomers, either spherically or cylindrically (vermiform) symmetric, is considered. The compactness of the polymer constitutive unit distribution, the branches and the backbone conformations are considered as functions of the first two parameters above. Significant results are obtained on all of these three points.
