Two‐Step Solvent‐Free Synthesis of Poly(hydroxybutyrate)‐Based Photocurable Resin with Potential Application in Stereolithography

Abstract

A bio‐based polymeric ink for stereolithography developed through a two‐step solvent‐free process is herein proposed. Specifically, low‐molecular‐weight poly(hydroxybutyrate) (PHB)‐diol oligomers are prepared via molten transesterification of bacterial PHB with 1,4‐butanediol. Transesterification conditions such as diol concentration, catalyst amount, and reaction time are studied for optimizing the final oligomers’ molecular weight and structural features. In the second step, the oligomeric hydroxyl terminals are converted into methacrylate moieties through a solvent‐free end‐capping reaction and diluted in propylene carbonate in order to obtain a photo‐polymerizable ink with suitable viscosity. The ink is UV‐cured, and the obtained material properties are investigated by FT‐IR and differential scanning calorimetry measurements. The proposed method provides a valuable and environmentally friendly alternative to currently available synthetic routes, overcoming their typical disadvantages related to the used solvents and harsh conditions. Moreover, it opens up a sustainable route for converting polyesters into functionalized oligomeric derivatives, which can potentially find application in 3D printing of customized biomedical devices.

Ring Opening Copolymerization of Four-Dimensional Printed Shape Memory Polyester Photopolymers Using Digital Light Processing

“…The peaks at 12.03 and 5.39 ppm indicate the presence of both carboxylic acid and alcoholic end groups, respectively, and the peaks in the 5 to 6 ppm region confirm the presence of both the allyl and cyclohexene functional groups within the polymer chain after polymerization (Supporting Information Figures 1−8), which could be leveraged for further reactions. As a representative case, 13 C NMR of poly(CyHene-co-AGE) (Supporting Information Figure 2) revealed peaks at 175.9, 175.5, and 174.6 ppm, indicating carboxylic acid end groups and ester linkages, as well as less-than-ideal selectivity in the polyester formation, an expected result when using stannous octoate as the catalyst. 56 AGE was polymerized into polyether derivative PEther(AGE) as reported elsewhere, and attempts to produce functionalized epoxide resulted in spontaneous ROPs at room temperature during photoirradiation and were therefore not explored further.…”

Levulinic acid-based bioplasticizers: a facile approach to enhance the thermal and mechanical properties of polyhydroxyalkanoates

“…Considering the narrow temperature range (approx. 20°C) where PHB can be processed without thermal degradation, 68 the observed decreases of T g and T m are remarkable results…”

Recent Advances in 3D Printing of Polyhydroxyalkanoates: A Review

“…Finally, PHB oligomers with methacrylate functionalities were obtained. This work showed that the developed methacrylated PHB oligomers were soluble in propylene carbonate at 90°C and after addition of photo-initiator were photo-polymerizable under UV light within 10 minutes (29).…”

“…(28). As crucial factors for the unproblematic SL process are considered the effective content of photo-sensible active terminating functional groups and the viscosity lower than 5 Pa.s (29). The typical stereolithographic prepolymers are acrylate monomers, methacrylate monomers, epoxides and vinyl ethers.…”