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Advisor(s)
Abstract(s)
Functionalized polyethylene-based nanocomposites were prepared by in situ polymerization of ethylene with modified or neat MCM-41 nanoparticles (NMCM-41). Two different synthetic
approaches were investigated to improve the compatibility between the hydrophobic HDPE matrix
and the hydrophilic NMCM-41: (i) incorporation of UA into the polymeric matrix by copolymerization with ethylene, promoted by the zirconocene catalyst under homogeneous conditions, in the
presence of pristine NMCM-41; (ii) use of undecenoic acid (UA) as an interfacial agent to obtain
decorated NMCM-41 to be used as nanofiller for the in situ ethylene polymerization, catalyzed by
Cp2ZrCl2/MAO under supported conditions. The strong polar character of the carboxylic group is
expected to either increase the hydrophilicity of the HDPE chains (strategy i) or interact with the
NMCM-41 surface and provide an additional link to the polymeric chains via copolymerization of
the vinyl group under supported conditions (strategy ii). Although metallocene catalysts have been
shown to copolymerize olefins with functional monomers, the presence of oxygen-containing compounds in the reaction media strongly affects the polymerization activity as a result of the interaction
of functional groups with the electrophilic active center of the catalyst. Thus, UA was pre-contacted
with tri(isobutyl)aluminum (TIBA) prior to its use in the polymerization to reduce the deactivating
character of the carboxylic acid groups towards the zirconocene catalyst. The influence of the UA
presence on the polymerization behavior of the protection step is discussed, and the polymerization
activities observed for the different approaches are compared. In addition, the thermal behavior
and structural details of the resulting materials have been characterized. The impact of using neat
or functionalized NMCM-41 on the final dispersion within the polymeric matrix is also analyzed,
which is correlated with the mechanical performance exhibited by these HDPE_UA_NMCM-41
nanocomposites.
Description
Keywords
Polyethylene Undecenoic acid MCM-41 Nanocomposites Dispersion Crystallinity Stiffness
Citation
Catalysts 13 (8): 1182 (2023)
Publisher
MDPI