Solvent-based synthesis, structural elucidation and thermal characterisation of free radical grafted PHBV

IF 6.3 2区化学 Q1 POLYMER SCIENCE Polymer Degradation and Stability Pub Date : 2024-08-23 DOI:10.1016/j.polymdegradstab.2024.110976

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Abstract

This study investigates the solvent-based free-radical graft copolymerization of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with C₁₁ (undecenoic acid, UDA), C₁₂ (dodecene, DD), and C₁₈ (octadecene, OD) alkene substrates using dicumyl peroxide as an initiator. Comprehensive Nuclear Magnetic Resonance (NMR) spectroscopy was employed to confirm and quantify grafting, which was achieved at up to 5.8 mol% of monomer units. Thermal analysis revealed a significant reduction in melting temperature for all modified PHBVs, ranging from 10-20°C decrease in comparison to virgin PHBV. A decrease in crystallisation temperature and a reduction in glass transition temperature was measured for the UDA and DD grafted PHBV. Additionally, molecular weight analysis showed a marked decrease in weight average molecular weight ( ${\bar{M}}_{w}$ ) and number average molecular weight ( ${\bar{M}}_{n}$ ) for PHBV grafted with UDA, which was attributed to the presence of carboxylic acid functionality, which accelerates chain scission. The molecular weight profiles of the dodecene and octadecene grafted PHBV were only marginally reduced (32% and 18% reductions in ${\bar{M}}_{w}$ , respectively), which is a much less severe reduction than has been previously observed for similar chemistries. Overall, this work demonstrates that solvent-based free-radical graft copolymerization can reduce the melting temperature and disrupt the crystallinity of PHBV, hence improving its processability and progressing the field of PHA modification and application.

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自由基接枝 PHBV 的溶剂型合成、结构阐释和热特性分析

本研究以过氧化二异丙苯为引发剂，研究了聚(3-羟基丁酸-3-羟基戊酸)（PHBV）与 C11（十一烯酸，UDA）、C12（十二烯，DD）和 C18（十八烯，OD）烯基的溶剂型自由基接枝共聚。采用全面的核磁共振 (NMR) 光谱来确认和量化接枝，单体单元的接枝率高达 5.8 摩尔%。热分析表明，与原始 PHBV 相比，所有改性 PHBV 的熔化温度都明显降低，降幅在 10-20°C 之间。UDA 和 DD 接枝 PHBV 的结晶温度降低，玻璃化温度降低。此外，分子量分析表明，UDA 接枝的 PHBV 重量平均分子量（M¯w）和数量平均分子量（M¯n）明显下降，这归因于羧酸官能团的存在加速了链的断裂。十二烯和十八烯接枝的 PHBV 的分子量仅略有降低（M¯w 分别降低了 32% 和 18%），这比以前在类似化学物质中观察到的降低幅度要小得多。总之，这项工作证明了基于溶剂的自由基接枝共聚可以降低 PHBV 的熔化温度并破坏其结晶性，从而改善其加工性能，推动 PHA 改性和应用领域的发展。

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来源期刊

Polymer Degradation and Stability 化学-高分子科学

CiteScore

10.10

自引率

10.20%

发文量

325

审稿时长

23 days

期刊介绍： Polymer Degradation and Stability deals with the degradation reactions and their control which are a major preoccupation of practitioners of the many and diverse aspects of modern polymer technology. Deteriorative reactions occur during processing, when polymers are subjected to heat, oxygen and mechanical stress, and during the useful life of the materials when oxygen and sunlight are the most important degradative agencies. In more specialised applications, degradation may be induced by high energy radiation, ozone, atmospheric pollutants, mechanical stress, biological action, hydrolysis and many other influences. The mechanisms of these reactions and stabilisation processes must be understood if the technology and application of polymers are to continue to advance. The reporting of investigations of this kind is therefore a major function of this journal. However there are also new developments in polymer technology in which degradation processes find positive applications. For example, photodegradable plastics are now available, the recycling of polymeric products will become increasingly important, degradation and combustion studies are involved in the definition of the fire hazards which are associated with polymeric materials and the microelectronics industry is vitally dependent upon polymer degradation in the manufacture of its circuitry. Polymer properties may also be improved by processes like curing and grafting, the chemistry of which can be closely related to that which causes physical deterioration in other circumstances.