Polymerisation Mechanisms

Polymerisation mechanisms fall into two broad categories: chain-growth and step-growth. In chain-growth processes, reactive centres (radical, ionic or coordination sites) add monomers rapidly at one end of a growing chain. Step-growth mechanisms rely on condensation or addition reactions between functionalised monomers or oligomers, with high conversion needed to reach useful molecular weights. Ring-opening polymerisation (ROP) employs cyclic monomers whose ring strain or entropy gain drives chain extension by radical, cationic or anionic initiators or via metathesis pathways (ROMP). Coordination polymerisation uses metal catalysts (Ziegler–Natta or single-site metallocenes) to insert olefins with control over stereochemistry and molecular weight. Photoinitiated routes harness light-activated species to generate radicals or ions, enabling spatial and temporal control, mild conditions and applications in coatings, adhesives and 3D printing.

Research from Nature Portfolio

Ultraviolet-blocking optically clear adhesives have been realised by a highly efficient visible-light curing system. By tuning photocatalyst and co-initiator interactions in the presence of UV absorbers, cure rates increased tenfold under LED illumination, while preserving transparency and flexibility. This advance addresses challenges in foldable-display encapsulation by enabling rapid, low-temperature photopolymerisation in formulations containing UV-scavenging agents.

Upconversion particle-assisted NIR polymerisation exploits lanthanide-doped nanoparticles that convert low-energy NIR photons into UV/visible light in situ. This localised activation yields domain-limited gradient polymer networks with reduced shrinkage stress and enhanced mechanical properties. The approach allows deep-cure of thick or filled systems under 980 nm laser irradiation, opening pathways for biomedical implants and stress-sensitive composites cured by NIR sources.

Research from all publishers

Transition metal complexes with long-lived excited states have emerged as potent visible-light photoinitiators for free-radical and thiol–ene polymerisation. Their redox reversibility delivers high monomer conversion under low-power LEDs, and integration into 3D-printing resins affords intricate architectures with energy-efficient curing and improved resolution.

Benzothioxanthene-based oxime esters, acting via photocleavage and single-electron transfer, enable photopolymerisation under household and solar light up to 600 nm. These dual-mechanism photoinitiators drive rapid cure under low-intensity LEDs and winter sunlight, with direct laser-writing experiments confirming sub-micrometre feature fidelity.

Reviewing anionic ROP of lactams, recent developments highlight catalysts and activators for in situ nylon-6 production in thermoplastic composite manufacturing. Control of moisture, initiator composition and mold temperature yields high-molecular-weight polyamide with tailored crystallinity and mechanical performance, supporting continuous, recyclable thermoplastic routes for automotive and aerospace applications.

Polymerisation Mechanisms publication trend

The graph below shows the total number of articles in polymerisation mechanisms across all publications each year (not limited to Nature Index journals).

Technical terms

Chain-growth polymerisation: Mechanism in which an active centre adds monomer units sequentially to one chain end.

Step-growth polymerisation: Process where bifunctional or multifunctional monomers react to form oligomers and polymers, requiring high conversion for high molecular weight.

Ring-opening polymerisation (ROP): Chain-growth of cyclic monomers driven by ring strain or entropy gain, initiated by radicals, cations, anions or metathesis catalysts.

Photoinitiator: Compound that absorbs light and generates reactive species (radicals or ions) to start polymerisation.

Coordination polymerisation: Olefin polymerisation mediated by transition-metal catalysts (Ziegler–Natta or metallocene) via monomer coordination and insertion into metal–carbon bonds.

References

1. Ultraviolet light blocking optically clear adhesives for foldable displays via highly efficient visible-light curing. Nature Communications (2024).
2. Upconversion particle-assisted NIR polymerization enables microdomain gradient photopolymerization at inter-particulate length scale. Nature Communications (2023).
3. Recent Advances of Transition Metal Complexes for Photopolymerization and 3D Printing under Visible Light. Advanced Functional Materials (2023).
4. High Photoinitiating Efficiency of Benzothioxanthene‐Based Oxime Esters in Photopolymerization via Photocleavage and/or Single Electron Transfer under Visible Light and Sunlight. Angewandte Chemie International Edition (2024).
5. Polymers and Related Composites via Anionic Ring-Opening Polymerization of Lactams: Recent Developments and Future Trends. Polymers (2018).
6. Polymer Synthesis.