Laboratorio de Química Sostenible, Departamento de Química Analítica, Facultad de Química, Universidad Nacional Autónoma de México, Apartado Postal 70-360, Ciudad Universitaria, Coyoacán, 04510, Ciudad de México, Mexico.
Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México. Ave. Universidad 3000. Col. UNAM. Coyoacán, 04510, Ciudad de México, Mexico.
Chemosphere. 2022 Nov;307(Pt 4):136136. doi: 10.1016/j.chemosphere.2022.136136. Epub 2022 Aug 23.
The presence of unsaturation in the main chain of the polymer promotes the biodegradation process. To elucidate this hypothesis, one unsaturated polyurethane (PUU) and another saturated polyurethane (PUS) were synthesized and then biodegraded, and evidence was found to support this hypothesis. The polyurethanes were synthesized by a polycondensation reaction with yields up to 97%. It is important to note that both polyurethanes were constituted only by the recalcitrant hard segment and showed low crystallinity and molecular weight. Spectroscopic, thermal, and chromatographic techniques were used for physical and structural characterization. Both polyurethanes were biodegraded by the BP8 microbial community and the Cladosporium tenuissimum A3.I.1 fungus during a two-month period. A postbiodegradation characterization revealed the detriment of properties in both materials, indicating successful biodegradation. As a general trend, more efficient biodegradation was observed by the Cladosporium tenuissimum fungus A3.I.1 than by the BP8 microbial community. Specifically, with the fungus, the infrared analysis showed a decrease in the characteristic bands as well as the appearance of new carboxylic acid signals (approximately 1701 cm), suggesting the enzymatic cleavage of the urethane group. By comparison to polyurethanes, PUU showed superior biodegradation; using the fungus, a 51% decrease in molecular weight (M) for PUU was achieved, in contrast with 36% achieved for PUS. Despite the low crystallinity and molecular weight, the determining factor in biodegradation was the presence of unsaturations along the main chain. Thus, a more efficient oxidative attack is carried out by microorganisms on double bonds. The novel PUU showed similar biodegradation to the known polyester-type PU with highly hydrolysable groups. Consequently, PUU represents a green alternative to conventional polyurethanes and is a key material to achieve biorecycling.
聚合物主链中存在不饱和键会促进其生物降解过程。为了阐明这一假设，我们合成了一种不饱和聚氨酯（PUU）和一种饱和聚氨酯（PUS），并对其进行了生物降解，结果发现有证据支持这一假设。通过缩聚反应合成了这两种聚氨酯，产率高达 97%。需要注意的是，这两种聚氨酯仅由难降解的硬段组成，结晶度和分子量都较低。采用光谱、热和色谱技术对其进行物理和结构表征。BP8 微生物群落和 Cladosporium tenuissimum A3.I.1 真菌在两个月的时间内对这两种聚氨酯进行了生物降解。生物降解后特性的变化表明这两种材料都发生了成功的生物降解。总的来说，Cladosporium tenuissimum A3.I.1 真菌的生物降解效率高于 BP8 微生物群落。具体来说，在真菌的作用下，红外分析显示特征谱带减少，出现新的羧酸信号（约 1701cm），这表明了氨酯键的酶促断裂。与聚氨酯相比，PUU 的生物降解性能更好；使用真菌时，PUU 的分子量（M）下降了 51%，而 PUS 的分子量下降了 36%。尽管结晶度和分子量较低，但决定生物降解的因素是主链上不饱和键的存在。因此，微生物对双键进行更有效的氧化攻击。新型 PUU 表现出与具有高度可水解基团的已知聚酯型 PU 相似的生物降解性。因此，PUU 是传统聚氨酯的绿色替代品，也是实现生物循环的关键材料。
