Abstract
In this study, a series of poly(l-lactide) and (3-amino)-propylheptaisobutyl cage silsesquioxane (PLLA-AMPOSS) intermediates were first fabricated using single-arm in situ solution polymerization of LLA monomers and AMPOSS nanoparticles with different contents, 0.02–1.00 mol%. Then, the PLLA-AMPOSS intermediate with 0.5 mol% AMPOSS was selected as a representative and investigated by nuclear magnetic resonance (NMR) and X-ray diffraction (XRD). Afterwards, it was added into the pure PLLA with different mass fractions. Finally, the thermal behavior, crystallization kinetics, morphological characteristics, and mechanical properties of the obtained PLLA/PLLA-AMPOSS nanocomposites were carefully measured and investigated by differential scanning calorimetry (DSC), polarizing microscopy (POM), scanning electron microscopy (SEM), and tensile test. After comparing the PLLA-AMPOSS intermediate and PLLA/AMPOSS blend, the results show that the ring-open polymerization of PLLA-AMPOSS intermediate was successful. The results also show that the existence of PLLA-AMPOSS has a strong influence on the crystallization behavior of PLLA/PLLA-AMPOSS composites, which can be attributed to the heterogeneous nucleation effect of PLLA-AMPOSS. In addition, it was also found from the tensile test results that the addition of the PLLA-AMPOSS nanofiller improved the tensile strength and strain at break of PLLA/PLLA-AMPOSS nanocomposites. All of these results indicate the good nucleating effect of PLLA-AMPOSS and that the AMPOSS disperses well in the PLLA/PLLA-AMPOSS nanocomposites. A conclusion can be drawn that the selective nucleating agent and the combined method of in situ ring-opening polymerization and physical blending are feasible and effective.
Highlights
It has been well realized that environmental pollution has become significantly serious nowadays, and it is partially caused by the abandoning of traditional nondegradable materials
Similar to other semicrystalline polymers, including isotactic polypropylene [13,14,15,16], polycaprolactone (PCL) [17], poly(vinylidene fluoride) (PVDF) [18], and poly(cyclohexylene dimethylene cyclohexanedicarboxylate) (PCCE) [19,20], controlling crystallization has gradually become known as an effective way to obtain the required performance of PLLA parts
In order to investigate the chemical structure and composition, 1H-nuclear magnetic resonance (NMR) spectroscopy was performed on the fabricated PLLA-AMPOSS intermediate, neat PLLA, AMPOSS, and simple blend of PLLA and AMPOSS, as shown in Figure 2a–d, respectively
Summary
It has been well realized that environmental pollution has become significantly serious nowadays, and it is partially caused by the abandoning of traditional nondegradable materials. Similar to other semicrystalline polymers, including isotactic polypropylene (iPP) [13,14,15,16], polycaprolactone (PCL) [17], poly(vinylidene fluoride) (PVDF) [18], and poly(cyclohexylene dimethylene cyclohexanedicarboxylate) (PCCE) [19,20], controlling crystallization has gradually become known as an effective way to obtain the required performance of PLLA parts These works can be roughly classified into three categories when considering large-scale industrial applications. By adjusting the substituents of the POSS cage block at the molecule level in the processes of copolymerization, polycondensation, homopolymerization, and physical blending, the intermediate and composited materials with required functionalization can be fabricated and manufactured in a controlled way. The mechanical properties of the obtained nanocomposite were tested and compared by the tensile test
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