Molecular dynamics in electrospun amorphous plasticized polylactide fibers

Abstract

is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. The molecular dynamics in the amorphous phase of electrospun fibers of polylactide (PLA) has been investigated using the cooperative rearranging region concept. An unusual and significant increase of the cooperativity length at the glass transition induced by the electrospinning has been observed. This behavior is attributed to the singularity of the amorphous phase organization. Electrospun PLA fibers rearrange in a pre-ordered metastable state which is characterized by highly oriented but non-crystalline polymer chains, and the presence of highly cohesive mesophase which plays the role of an anchoring point in the amorphous phase. The successful processing of electrospun fibers of plasticized polylactide is also demonstrated. It is shown that the plasticizer remains in the polymer matrix of the nanofiber after electrospinning. When PLA is plasticized, the loosening of the macromolecules prevails over the preferential orientation of the chains; therefore no mesophase is formed during the electrospinning and the cooperativity length remains the same. When the content of plasticizer increases, the inter-chain characteristic distances estimated from wide angle X-ray scattering (WAXS) are redistributed, suggesting a change in the level of interactions between macromolecules. It is assumed that the resulting decrease of the cooperativity length is driven by the progressive reduction of the number of inter-chain weak bonds. It is shown that in a non-confined environment, the number of structural entities involved in the alpha relaxation is strongly dependent on the level of physical interactions in the amorphous phase.

A structural interpretation of the two components governing the kinetic fragility from the example of interpenetrated polymer networks

“…The decrease of the CRR size under confinement has been reported for nanoparticles, nanolayers, intercalated nanocomposites, and semicrystalline polymers . Any modification of the intermolecular bonds may also impact the cooperativity, as observed in plasticized polylactide, when electro‐donor and electro‐acceptor side groups are associated in statistical methacrylate copolymers, or when π‐stacking is hindered in polycarbonate . Nakanishi and Nozaki proposed a simplified model of hydrogen‐bonding network that supports the increase in the CRR size with intermolecular bonds.…”

Fabrication of ceramic nanofibers using polydimethylsiloxane and polyacrylonitrile polymer blends

“…All the mentioned research utilizes silicon polymers to manufacture ceramics, some of them use polymer combinations (copolymers) to fabricate ceramics. For instance, Monnier et al …”

Local and segmental motions of the mobile amorphous fraction in semi-crystalline polylactide crystallized under quiescent and flow-induced conditions

“…The pellets were then thermo-compressed between two hot plates during 5 min at a pressure of 1 bar and a temperature of 180 °C. The temperature was selected below the equilibrium melting temperature T m 0 (ranging from 199 °C to 207 °C [56] ) and above the nominal melting temperature T m (ranging from 160 to 170 °C [57,58] ). The samples were then quickly quenched in cold water and dried, obtaining self-standing films with thicknesses ranging between 200 and 300 μm.…”

“…Sample mass was estimated from the step change in heat flow at the glass transition: the heat capacity step ΔC p obtained by FSC at lβ c l = β h = 1500 K s -1 was compared to the value obtained by conventional DSC at lβ c l = β h = 0.17 K s -1 , that is to say 0.51 J/(g.K) for a completely amorphous PLA according to the literature. [58] Before FSC experiments, the shape of the samples was observed by optical microscopy on a microscope cover-glass in transmission mode. After FSC experiments, the shape of the samples adhered on the chip sensor was examined in reflection mode.…”

“…Due to their metastability, the existence of shear-induced precursors is time and temperature dependent, as already observed for other polymers such as PP, PBu, PEO or PS. [11,12] In this work, the lifetime and relaxation behavior of PLA shear-induced precursors was investigated in the temperature range where melting of semicrystalline PLA is typically reported [57,58] to mimic flow conditions typical of industrial processing. The relaxation temperature map in Fig.…”