Poly(glycolide) multi-arm star polymers: Improved solubility via limited arm length

Area of Science:

• Polymer Chemistry
• Materials Science
• Biomedical Engineering

Background:

• Poly(glycolic acid) (PGA) exhibits low solubility, limiting its use to specific applications or random copolymers.
• High molecular weight PGA (degree of polymerization > 20) is typically insoluble, restricting processing options.

Purpose of the Study:

• To develop a strategy for synthesizing high-molecular-weight, soluble PGA-based multi-arm structures.
• To overcome the solubility limitations of poly(glycolic acid) for broader applications.

Main Methods:

• Utilized a multifunctional hyperbranched polyglycerol (PG) as a macroinitiator.
• Employed tin(II)-2-ethylhexanoate catalyzed ring-opening polymerization of glycolide in the melt.
• Characterized the resulting star block copolymers using NMR and SEC.

Main Results:

• Successfully synthesized PGA multi-arm star block copolymers with high molecular weights (up to 16,000 g/mol) and good control (PDI = 1.4-1.7).
• Achieved over 90 wt% of glycolide in the final copolymers.
• Demonstrated solubility in DMF and DMSO for materials with average arm lengths up to 12 glycolic acid units.
• Observed reduced glass transition temperature (T(g)) and melting temperature compared to homopolymer PGA.

Conclusions:

• The core-first/grafting-from strategy enables the creation of high molecular weight, soluble PGA star polymers.
• These novel materials offer improved processability and potential for expanded use in biomedical fields.
• The study broadens the scope of poly(glycolic acid) applications through advanced polymer architecture.