The Influence of Graft Length and Density on Dispersion, Crystallisation and Rheology of Poly(ε-caprolactone)/Silica Nanocomposites

Abstract

Different techniques of grafting polymer chains to filler surfaces are often employed to compatibilise filler and polymer matrices. In this paper the influence of graft length and graft density on the state of dispersion, crystallisation and rheological properties of poly(ε-caprolactone) (PCL)/silica (SiO2) nanocomposites are reported. Grafted silica nanoparticles were prepared through polymerisation of PCL from the nanoparticle surface. Graft length was controlled by the reaction time, while the grafting density was controlled by the monomer-to-initiator ratio. Grafted nanoparticles were mixed with PCL of different molecular weights and the state of dispersion was assessed. Different matrix-to-graft molecular weight ratios resulted in different states of dispersion. Composites based on the higher molecular weight matrix exhibited small spherical agglomerates while the lower molecular weight matrix revealed more sheet-like microstructures. The state of dispersion was found to be relatively independent of graft length and density. Under quiescent conditions the grafts showed increased nucleation ability in the higher molecular weight PCL, while in the lower molecular weight matrix the effect was less pronounced. Rheological experiments showed an increase in viscosity with increased filler content, which was beneficial for the formation of oriented structures in shear-induced crystallisation.

Flowerlike Multipetal Structures of Nanoparticles Decorated by Amphiphilic Homopolymers

“…To validate the theoretical model and compare analytical and simulation data, the structure diagram in variable grafting density ρ gr = Mv 2/3 /16r 2 vs nanoparticle radius r was constructed (Figure 8) for different polymerization degrees, N. As described above, the stability region of a particular structure was determined by a comparison of the free energies of different structures F (k) /MN (K = 1, ..., 4) per monomer unit. But in this case, the free energies F (k) /MN (K = 2, ..., 4) of structures with two and more petals were calculated using the complete expression of the free energy (12) with k 1 = −1, k 2 = 1, and k G = −1.…”

“…Structure Diagrams. In the limiting case with MN ≫ 1 and a small petal curvature (large R values), the last two terms in (12) are insignificant in comparison with the first three terms, and the free energy can be rewritten as…”

“…Spherical nanoparticles decorated by grafted macromolecules are promising for broad application in diverse high-tech fields, including drug-delivery systems in personal medicine and eco-friendly methods of oil production. − They are the subject of a huge number of experimental, − computer, − and theoretical − studies.…”

Effect of OMMT reinforcement on morphology and rheology properties of polyurethane copolymer nanocomposites

“…The increase of G 0 and G 00 is basically greater for PUC/OMMT nanocomposites when compared to their neat PUC/75 counterparts due to the state of the better filler-polymer bonding and particle-particle interactions. 47,48 This could be an effect of the OMMT-PUC interfacial interaction, homogeneity dispersion, and larger surface area of clay particles exposed to the polymer chains. 5 The low frequency region of the rheological curve indicates the intercalated effect of OMMT on the G 0 and G 00 of PUC/OMMT nanocomposites in comparison with G 0 and G 00 of neat PUC/75.…”

Synthesis and characterization of poly(L‐lactide)‐block‐poly(ε‐caprolactone)‐grafted titanium dioxide nanoparticles via ring‐opening in situ grafting polymerization

“…The ring-opening polymerization method has been used successfully in the grafting process. For instance, grafting of PLA from cellulose nanocrystals, [33] graphene oxide, [34] chitosan, [35] nano-TiO 2, [36] and PCL from polydopamine, [37] starch, [38] carbon nanotube, [39] silicate nanoparticles, [40] and silica [41] nano-TiO 2 [42] have been studied. Despite various studies on grafting polymerization methods from several materials, the polymerization of PLLA-b-PCL from TNP has not been studied.…”