**5. Conclusions**

Polylactide nanocomposites, composites, and blends containing specific organic compounds (arylamides and arylhydrazides, 1,3:2,4-dibenzylidene-d-sorbitol, or orotic acid), humic and fulvic acids, nanocellulose, and cyclodextrins have been reviewed. Supramolecular interactions operating in those blends play a very important role in the properties of those novel hybrid materials. They di ffer from other PLA-based hybrids containing inorganic additives or composites of PLA and graphene or carbon nanotubes.

Aryl nucleators containing amide or hydrazide linkages are capable of crystallization in the polylactide melt. The formation of nanofibrils/nano-objects upon the self-organization of these moieties exploits two recognition motifs: hydrogen bonds and π-π interactions between the molecules taking part in the formation of supramolecular structures and intermolecular hydrogen bonds linking those formations and the polyester backbones. Macromolecular nucleators (humic/fulvic acids and nanocellulose) not only help in the formation of crystal nuclei but also improve the mechanical

properties of the PLA. Host–guest e ffects in blends containing inclusion complexes of PLA and (α/β/γ)-cyclodextrins change the mobility of the polyester chains. The formed structures may also enhance the polylactide crystal growth, but they have much larger potential. Treading cyclodextrins onto PLLA backbones may be used for the design of biocompatible molecular rotors. Interestingly, chiral recognition was observed for the PLLA/PDLA mixtures and α-CD.

The performance of PLA can be improved because of those specific interactions that modify the organization of the polymer matrix. The "soft templating" may change the conformation of segments in PLA chains and influence the nucleation of polymer crystals, thus enormously enhancing the crystallization process. Despite the templating, the type of crystal structure is not changed, except that the well-organized α-crystals are more easily formed in such systems. The influence of supramolecular nucleators is of exceptional importance, as the crystallinity of PLA plays a significant role in its mechanical and barrier properties, biodegradability, and thermal stability. Many supramolecular systems described in this review are biocompatible and can be used for biomedical purposes.

**Author Contributions:** Conceptualisation, writing—original draft preparation, and funding acquisition, A.K.; writing—review and editing, M.N. All authors have read and agreed to the published version of the manuscript.

**Funding:** The APC was funded by Polish National Centre of Sciences (NCN) gran<sup>t</sup> No 2016/21/B/ST5/03070.

**Conflicts of Interest:** The authors declare no conflict of interest.
