Photoinduced Degradation of Polymer Films Using Polyglyoxylate–Polyester Blends and Copolymers

Abstract

Polymeric coatings are commonly employed to alter surface properties. While some coatings are designed to remain stable over a prolonged period, in applications such as pharmaceuticals or fertilizers, the coating is designed to erode and reveal or release the underlying material. Self-immolative polymers (SIPs) undergo depolymerization following the cleavage of stimuli-responsive end-caps from their termini, enabling controlled depolymerization in the solid state and in solution. Poly(ethyl glyoxylate) (PEtG) is a promising SIP because of its depolymerization to benign products, but its amorphous structure and low glass-transition temperature make it unsuitable alone for coating applications. This study explored the blending of PEtG with polyesters including polycaprolactone (PCL), poly( l -lactic acid), and poly( R -3-hydroxybutyrate). Block copolymers of PEtG with PCL were also synthesized and studied. It was found that the phase separation behavior and consequently the thermal and mechanical properties of the materials could be tuned according to the composition of the blend, while the stimuli-responsive degradation of PEtG was retained in the blends. This work therefore provides a framework for the application of PEtG-based coatings in applications ranging from pharmaceuticals to agricultural products.

Polyglyoxylamides with a pH-Mediated Solubility and Depolymerization Switch

“…An M n of 22 kg/mol was targeted as this chain length allows for wellcontrolled polymerization and easy isolation of the resulting polymer by precipitation in cold methanol. The resulting polymer (PEtG-1) was characterized by 1 H NMR, 13 C NMR, and FT-IR spectroscopic methods, confirming its identity as well as the presence of the alkyne moiety at the terminus (Figures 2, S1, and S10). SEC in DMF revealed that the polymer had an M n of 17.8 kg/mol and Đ of 1.7 relative to PMMA standards (Table 1).…”

“…1 H and 13 C NMR spectra were obtained using one of the following instruments: 400 MHz Bruker AvIII HD, 400 MHz Varian INOVA, or 600 MHz Varian INOVA. 1 H NMR chemical shifts were calibrated against the residual solvent signal of CHCl 3 (7.26 ppm) or HOD (4.79 ppm), while 13 C NMR chemical shifts were calibrated against the solvent signal of CDCl 3 (77.16 ppm). FT-IR spectra were obtained using a PerkinElmer FT-IR Spectrum Two instrument with attenuated total reflectance (ATR) sampling.…”

“…To obtain PGAms with lower solubility at neutral pH, the more hydrophobic N,Ndiethylethylenediamine and N,N-diisopropylethylenediamine were investigated to yield PGAm(DEAE) and PGAm(DPAE), respectively. 1 H NMR, 13 C NMR, and FT-IR spectroscopy were used to characterize the new polymers (Figures 2, S2−S4, and S11−S13). The SEC results showed a decrease in retention time between the original PEtG-1 and PGAm-(DMAE), as expected due to the latter's increased molar mass (Table 1, Figure S20).…”

“…Self-immolative polymers (SIPs) are a class of degradable polymers that undergo end-to-end depolymerization to small molecules after the cleavage of their backbone or stabilizing end-cap by a stimulus. − Unlike traditional degradable or stimuli-responsive polymers, only a single bond cleavage is needed to initiate complete SIP degradation. This property makes SIPs attractive for applications such as sensing, , patterning, − degradable/recyclable plastics, − and drug delivery, − where an amplified or highly sensitive response to stimuli is desired. Several SIP backbones have been developed, including poly­(benzyl carbamates), , poly­(benzyl ethers), poly­(acetals), − poly­(olefin sulfones), , and more recently poly­(benzyl esters), polythioesters, , polycarboxypyrroles, polycyclopentenes, and polydisulfides .…”

Post-polymerization ‘click’ end-capping of polyglyoxylate self-immolative polymers

“…2 Additionally, a wide range of trigger endcaps have been reported to date, allowing SIPs to degrade in response to various environmental, chemical, and biological stimuli. 3 These unique properties of SIPs have fueled interest for their use in controlled release systems, [4][5][6][7][8][9][10] stimuli-respon-sive coatings, 11,12 chemical sensors, [13][14][15] and degradable bulk materials. [16][17][18] Since their debut in 2008, 19 a handful of SIP designs have been reported with degradation mechanisms based on 1,4and 1,6-elimination reactions of aromatic compounds, [20][21][22] heterocyclization reactions, 23,24 olefin sulfone elimination reactions, [25][26][27] and the depolymerization of polyacetals.…”