# Silica-Supported Zinc(II)–Schiff-Base Catalysts for Lactide Ring-Opening Polymerization: Influence of Support Morphology and Ligand Substituents

## TL;DR

This paper explores how the shape and structure of silica supports affect the performance of zinc-based catalysts in making biodegradable plastics from lactide.

## Contribution

The study introduces a new class of silica-supported zinc(II)–Schiff-base catalysts and shows how support morphology influences polymerization performance.

## Key findings

- Silica-gel-supported catalysts showed high and reproducible activity in lactide polymerization.
- Catalysts on silica nanoparticles were more sensitive to reaction time and ligand effects.
- The study confirmed the formation of atactic and stereoregular PLA from different lactide isomers.

## Abstract

Silica-supported zinc (II)–Schiff-base complexes were prepared through a simple and high-yield immobilization strategy and evaluated as heterogeneous catalysts for the ring-opening polymerization (ROP) of lactide. Silica gel and silica nanoparticles were employed as supports to assess the influence of support morphology and textural properties on catalytic performance. Comprehensive characterization by AAS, BET, SEM, and SEM–EDS confirmed effective anchoring of the Zn complexes, homogeneous metal distribution, and support-dependent textural modifications. The supported catalysts were active in the bulk ROP of racemic and enantiopure lactide, affording PLA with high conversions and moderate dispersities. Silica-gel-supported systems exhibited high and reproducible activity over a wide range of conditions, whereas catalysts supported on silica nanoparticles showed a stronger dependence on reaction time and ligand electronic effects, highlighting the key role of the support in modulating active site accessibility and chain growth. Microstructural and thermal analyses confirmed the formation of atactic PLA from rac-lactide and stereoregular PLLA from L-lactide. Overall, this study demonstrates that silica-supported zinc(II)–Schiff-base complexes constitute an effective and versatile heterogeneous platform for lactide ROP and underscore the importance of support properties in the rational design of sustainable catalysts for biodegradable polyester synthesis.