Self-assembly of polyesters like PLLA and PDLA into stereocomplexes (SCs) is an interesting approach to tailor physical properties of polymeric nanoparticles without affecting their hydrophilicity. Here, we use the stereocomplexation of P(LLA-stat-EtGly) and P(DLA-stat-EtGly) (EtGly: 3-ethylglycolide) to tune the melting temperature (T m ) and degree of crystallinity (w c ) of the bulk polymer. Using time-dependent blending experiments and characterization techniques, such as dynamic light scattering, wide-angle X-ray spectroscopy, differential scanning calorimetry, and atomic force microscopy, we tested the hypothesis that the amount of SCs within the nanoparticles impacts their mechanical properties. Our results show that T m and w c can be adjusted via the EtGly content. Interestingly, mechanical properties of the nanoparticles depend on the EtGly content as well as the self-assembly time of SCs before nanoparticle formation. This offers a high potential for their application in drug delivery, where their tunable properties will allow to adjust degradation and drug release behavior.
To obtain a set of
polycaprolactones (PCL) with varying crystallinity, the triazabicyclodecene-catalyzed
copolymerization of the two constitutional isomers ε-caprolactone
(εCL) and δ-caprolactone (δCL) was carried out at
room temperature in toluene. Variation of the feed fraction of εCL
from 50% to 80% and the detailed kinetic studies accompanied by application
of terminal as well as nonterminal kinetic models suggested the formation
of random copolymers. Differential scanning calorimetry and wide-angle
X-ray scattering investigations revealed the decrease of melting temperatures
and degree of crystallinity with the εCL fraction in the PCL.
All copolymers were suited to obtain aqueous nanoparticle dispersions
by means of nanoprecipitation. Encapsulation of the fluorescent probe
pyrene confirmed a constant hydrophilic/hydrophobic balance of the
nanoparticles.
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