Solvent-Induced Crystallization in Biodegradable Polymers

Solvent-induced crystallization employs selective solvents or solvent vapours to promote the organisation of polymer chains into ordered, crystalline domains within biodegradable matrices. By swelling the amorphous regions, solvents reduce chain mobility barriers and facilitate nucleation and growth of lamellar or spherulitic structures. Control over solvent type, concentration, temperature and exposure time allows tailoring of crystallinity, pore architecture and mechanical properties without high-temperature annealing. This approach has found application in porous scaffolds for tissue engineering, transparent films for packaging, controlled-release devices and agricultural mulches. The resulting semicrystalline morphology influences hydrolytic degradation rates, barrier performance and optical clarity, offering a sustainable route to high-performance biopolymers. Key challenges include solvent recovery, reproducibility at scale and optimisation of environmental impact.

Research from Nature Portfolio

Recent studies have demonstrated that thermally induced phase separation of poly(lactic acid) using a ternary solvent–non-solvent system can yield highly porous foams with tunable crystallinity and surface area. A mixture of tetrahydrofuran and water is used to dissolve the polymer, then exchanged with ethanol as a non-solvent before vacuum drying. Systematic variation of polymer concentration, solvent composition, quench temperature and ageing time, analysed via response surface methodology, enables precise control of pore size (down to ≈38 µm), foam density and Brunauer–Emmett–Teller surface area (up to 18.8 m2/g). This solvent-driven route offers a scalable platform for producing biodegradable scaffolds and filtration media with optimised mechanical strength and degradation behaviour.

Research from all publishers

Investigations into solvent-supported crystallization of semi-crystalline poly(l-lactide) sheets have shown that organic solvents with solubility parameters close to the polymer, such as ethyl acetate, o-dichlorobenzene and nitrobenzene, drive chain mobility and crystal formation. The degree of swelling, solvent evaporation rate, treatment temperature and exposure time collectively determine the extent of crystallinity, unit-cell dimensions and orientation of lamellar crystallites, as revealed by X-ray diffraction, differential scanning calorimetry and polarised-optical microscopy. Vapour-phase crystallization of amorphous poly(lactic acid) by acetone demonstrates that high crystallinity (~40%) and optical transparency can be achieved within 30 minutes at room temperature, with Fickian diffusion of vapour controlling kinetics. In a different polymer system, solvent-rich solutions of poly(butylene succinate) in N,N-diethyl-3-methylbenzamide undergo spherulitic crystallization upon cooling. Cloud-point measurements and differential scanning calorimetry reveal that increasing repellent content and cooling rate lower the crystallization temperature, while scanning electron microscopy shows that polymer concentration and quench temperature govern spherulite size, inter-spherulitic intermeshing and micro-porosity—key parameters for controlled-release matrices.

Solvent-Induced Crystallization in Biodegradable Polymers publication trend

The graph below shows the total number of articles in solvent-induced crystallization in biodegradable polymers across all publications each year (not limited to Nature Index journals).

Technical terms

Solvent-induced crystallization: A method in which a solvent swells the amorphous regions of a polymer, reducing the energy barrier for chain ordering and promoting crystal nucleation and growth.

Thermally induced phase separation (TIPS): A process where a homogeneous polymer solution separates into polymer-rich and polymer-lean phases upon cooling, leading to porous structures after solvent removal.

Spherulite: A spherical aggregate of radially growing polymer lamellae that forms during crystallization, often visible under polarised light microscopy.

Non-solvent: A liquid that does not dissolve the polymer but can replace the solvent in a gel, facilitating phase separation and pore formation.

Brunauer–Emmett–Teller (BET) surface area: A measure of specific surface area obtained by gas adsorption, indicative of the porosity and internal surface of a material.

References

1. Tuning pore size and density of rigid polylactic acid foams through thermally induced phase separation and optimization using response surface methodology. Scientific Reports (2024).
2. Temperature and Time Dependence of the Solvent-Induced Crystallization of Poly(l-lactide). Polymers (2020).
3. Crystallization of Amorphous Poly(Lactic Acid) Induced by Vapor of Acetone to Form High Crystallinity and Transparency Specimen. Open Journal of Polymer Chemistry (2013).
4. Phase behavior of solvent-rich compositions of the polymer/drug system poly(butylene succinate) and N,N-diethyl-3-methylbenzamide (DEET). Colloid and Polymer Science (2021).