The widespread utilization of nonrenewable fossil-based polymers has led to significant environmental damage. Bio-based Poly(lactic acid) (PLA) has garnered substantial academic and industrial interest in the last two decades due to its advantageous characteristics for food packaging applications. Nonetheless, the improper disposal of PLA continues to contribute to the plastic waste problem. PLA recycling mainly involves thermal processes, facing challenges due to PLA’s limited stability. This study aims to enhance PLA’s molecular weight and melt viscosity by using chain extenders to increase its degree of branching. A modular chain extender capable of thermally forming highly reactive ketene intermediates is employed to react with PLA’s hydroxyl and carboxyl end groups in a single step. For this purpose, copolymers of styrene and 2,2,5-trimethyl-5-(4-vinylbenzyl)-1,3-dioxane-4,6-dione were synthesized using free radical polymerization and characterized through 1H-NMR, TGA, and DSC analyses. The chemical interaction between these chain extenders and molten PLA was also explored, resulting in increased PLA molecular weight and higher melting temperature (Tm), reaching 155.1 for PLA_2.5CE2. Additionally, the branching introduced through this process led to a notable increase in the UV absorption of PLA, suggesting potential applications in the packaging industry. The chemical tunability of this functional ketene-based chain extender holds promise for tailoring PLA’s structure for diverse applications, further advancing its sustainability and utility.

Poly(ethylene terephthalate) (PET) is a widely used thermoplastic polymer with exceptional properties, making it a cornerstone in various industries. However, the extensive global demand for PET, particularly in the packaging sector, has led to significant ecological concerns due to inadequate recycling rates. This paper explores the potential of Meldrum's acid-based chain extenders as a solution to enhance PET recycling. Initially, 2,2,5-trimethyl-5-(4-vinylbenzyl)-1,3-dioxane-4,6-dione (St-MA) was synthesized, and its homopolymers were produced through free radical polymerization and characterized through H-1 NMR, FTIR and TGA analyses. Dynamic interactions between recycled PET (rPET) and the synthesized chain extender (HP) in an extrusion environment was further explored, resulting in higher T-g and T-c for rPET when 0.5 wt% of HP was added as a reactive chain extender. The chemical tunability of this functional ketene-based chain extender holds promise to enhance PET recycling practices. The continuous evolution of regulatory frameworks and environmental concerns may prompt the exploration of novel approaches, such as tailored Meldrum's acid-bearing chain extenders, which might have the potential to reduce the ecological consequences associated with post-consumer PET waste.

Melt processing of cellulose nanocrystals (CNCs) reinforced nanocomposites is still a serious challenge due to the hydrophilic nature of CNCs and their severe agglomeration tendency within the polymer melt. In this study, chemical modification of CNC through grafting poly(glycidyl methacrylate) (PGMA) with various degrees was implemented. Wettability of the modified CNCs (mCNCs) were controlled and their structure was characterized through Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), optical microscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The nanocomposites of polybutylene adipate terephthalate (PBAT) with 3 wt% CNC and mCNC were prepared using an internal melt mixer. To differentiate the effects of CNC and PGMA molecules on the final properties of nanocomposites, PBAT/PGMA compounds were separately prepared. To confirm the chain characterization and molecular weight of the synthesized PGMAs, 1H NMR and gel permeation chromatography (GPC) analysis were conducted. Melt rheological analysis, dynamic mechanical analysis (DMA), DSC, and atomic force microscopy (AFM) were used to monitor the mCNC dispersion quality and the effect of PGMA modification in PBAT compounds. The results revealed that grafting CNC with longer PGMA considerably improved the CNCs' dispersion quality within PBAT. Such dispersion enhancement of long-chain mCNCs and interfacial interaction of PGMA and PBAT resulted in a noticeable increase in storage modulus and complex viscosity of the final nanocomposites.

The development of biobased and environmental-friendly polymeric materials to replace petroleum-based plastics is one of the main global challenges nowadays. Among biopolymers, polyhydroxyalkanoates (PHAs) have gained increasing attention due to their compostability under environmental conditions. Copolymers of poly(3-hydroxybutyrate) (PHB) with comonomers belonging to PHA types have been developed to tackle better processability, higher ductility, and better impact properties. These common copolymers could be listed as poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH). Compared to PHB and PHBV, PHBH has revealed a wider processing window with better thermal stability and more promising mechanical performance due to its tailorable composition of both highly crystalline (3HB) and elastomeric (3HH) units. The increase in 3HH unit content decreases the crystallinity and the melting temperature, which broadens the processing window with minimized thermal degradation. Therefore, PHBH could be employed in applications where both flexibility and room temperature compostability are required. However, PHBH has received minimal attention due to its low availability in the market, high cost, strict confidentiality of the polymer manufacturers, and continuous evolution in the synthesis stage. This article reviews the achievements in PHBH synthesis and the dependency of PHBH thermal, mechanical, and physical properties on the 3HH content. It also explores PHBH compostability and degradation behavior and the attempts made to develop PHBH based blends and composites. It further discusses the challenges and future perspectives for the usage of PHBH in various industrial applications.

In this study, the composition of polylactide (PLA)/thermoplastic polyurethane (TPU) emulsion blends compatibilized with multifunctional epoxy-based Joncryl chain extender was regulated to tackle high impact resistant structures with improved ductility. PLA/TPU blends at different blending ratios of 95wt/05wt, 85wt/15wt, 75wt/25wt, and 65wt/35wt were first melt blended with 0.5 wt% of Joncryl. In all compositions, although the TPU droplets were significantly refined with the addition of Joncryl, the impact strength and ductility of the blends increased dramatically only at 75wt/25wt and 65wt/35wt blending ratios. The 75wt/25wt blend was then melt blended with various Joncryl contents of 0.25, 0.5, 0.75, and 1.0 wt%. It was illustrated that 0.5 wt% Joncryl was high enough to reach a blend with the highest impact strength and ductility of around 110 kJ/m(2) and 150%, respectively. This was while the tensile strength and modulus values remained comparable with those of neat PLA. The rheological experiments and the dynamic mechanical analysis confirmed that the complex viscosity and the storage modulus of the compatibilized blends were improved as a result of increased melt strength of PLA and the interfacial compatibilization through using Joncryl.

This study investigates the effect of using a multifunctional epoxide chain extender (Joncryl® ADR 4468) on the thermal stabilization and rheological properties of recycled polyethylene terephthalate (R-PET) and its blends with polybutylene terephthalate (PBT). The R-PET samples were prepared without and with chain extender (CE) contents of 0.4 wt% and 0.8 wt%. R-PET/PBT blends with weight ratios of 75w/25w, 50w/50w and 25w/75w were also prepared without and with a given CE content of 0.2 wt%. The thermal stability of the melt blended samples was analyzed through small amplitude oscillatory shear (SAOS) rheological experiments. The structure of the samples was evaluated using a Fourier transform infrared (FTIR) spectrometer. While the dynamic rheological properties of R-PET were improved with the addition of Joncryl and by blending with PBT, during the SAOS rheological experiments, the complex viscosity of R-PET further increased due to the concurrent polycondensation of R-PET and the resumption of Joncryl reaction with R-PET molecules. These reactions during the rheological experiments were further expedited with increasing the testing temperature. On the other hand, in R-PET/PBT blends, the reactivity of Joncryl was more noticeable in blends with higher R-PET contents due to the higher available internal reactive sites of much shorter R-PET molecules. It was observed that the addition of only 0.2 wt% Joncryl to the blends of R-PET/PBT (75w/25w) dramatically improves the thermal stability and dynamic rheological properties of R-PET and most likely its processability.

This study investigates the influence of using multifunctional epoxy Joncryl ADR 4468 chain extender (CE) on the properties of various polylactide (PLA)/thermoplastic polyurethane (TPU) (75 wt/25 wt) blend systems. The blends were based on two different TPU grades with ether- and ester-based soft segment as the dispersed phase (i.e., TPUether and TPUester) and an amorphous and a semicrystalline PLA grades as the matrix (i.e., aPLA and scPLA). PLA appeared to be more compatible with the TPUester, which caused the enhancement of the impact strength and strain at break values of the blends more remarkably. The dynamic rheological experiments also confirmed that the CE revealed a better reactivity with TPUester than TPUether. This further enhanced the interfacial compatibility between the PLA and TPUester and thereby dramatically improved the impact strength and ductility of the PLA/TPUester blends, specifically those with 0.5 wt% CE. Meanwhile, aPLA as the matrix reflected the TPUs toughening effect more efficiently than scPLA. This was due to the possible shrinkage caused by the crystallization of scPLA matrix, which could deteriorate the interfacial interactions between the phases in the corresponding blends.

The degradation behaviors of an amorphous and a semicrystalline PLA (i.e., aPLA and cPLA) with similar molecular weights are compared at elevated temperatures and after being treated under various environmental conditions through using small amplitude oscillatory shear rheological experiments. The degradation behaviors are also studied by differential scanning calorimetry and Fourier-transform infrared spectroscopy analysis. Melt thermal degradation analysis shows that the d-lactic acid content does not affect the degradation behavior of PLAs. This is while the increase in temperature beyond 190 °C dramatically, but still similarly, increases the degradation rate of aPLA and cPLA samples. It is also shown that processing of aPLA through a twin-screw extruder at temperatures below 190 °C and at different screw speeds has a negligible effect on its thermal degradation. The degradation of the PLA samples treated under various humidity levels as well as when exposed to different environments such as tap and sea water, regular garden soil and commercial grade microbial fertilizer, is expedited more dramatically around and beyond the glass transition temperature. This is while the cPLA, with around 50% crystallinity, reveals a much less degradation under the aforementioned conditions. This is because the bulk diffusion of water molecules or micro-organisms is harder in cPLA with a compacted crystalline structure. It should, however, be emphasized that the fertilizer degrades the PLA samples much faster and more pronounced than other environments. The tap and sea water exhibits a similar effect on the degradation of PLA samples. Notably, the temperature is the most effective parameter in expediting the degradation rate of PLA, suggesting that the PLA degradation could gradually occur in the environments with extreme warm weather. The increase in humidity also accelerates such degradation.

ABSTRACT A modular approach for the synthesis of graft copolymers by the combination of reversible addition–fragmentation chain‐transfer (RAFT) polymerization and photoinduced acylation processes is described. In the two‐step approach, first the copolymers of benzodioxinone containing monomer, namely, 4‐oxo‐2,2‐diphenyl‐4H‐benzo[d][1,3]dioxin‐7‐yl methacrylate (BDMA) and methyl methacrylate (MMA) in different feed ratios were prepared by RAFT polymerization. In the subsequent step, dichloromethane solutions of these copolymers (PMMA‐ co ‐PBDMA) were irradiated at λ = 300 nm in the presence of independently prepared hydroxyl functional polymers such as poly(ethylene glycol) (MeO‐PEG‐OH) and poly(ɛ‐caprolactone) (PCL‐OH). Side‐chain esterification reaction between photochemically generated ketene groups and hydroxyl functionalities resulted in the formation graft copolymers. The intermediates and final graft copolymers were characterized by 1 H NMR, UV, IR, fluorescence, and GPC measurements. The success of the process was also confirmed by a model reaction using pyrene methanol. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57 , 274–280

ABSTRACTA versatile strategy for the preparation of end‐functional polymers and block copolymers by radical exchange reactions is described. For this purpose, first polystyrene with 2,2,6,6‐tetramethylpiperidine‐1‐oxyl end group (PS‐TEMPO) is prepared by nitroxide‐mediated radical polymerization (NMRP). In the subsequent step, these polymers are heated to 130 °C in the presence of independently prepared TEMPO derivatives bearing hydroxyl, azide and carboxylic acid functionalities, and polymers such as poly(ethylene glycol) (TEMPO‐PEG) and poly(ε‐caprolactone) (TEMPO‐PCL). Due to the simultaneous radical generation and reversible termination of the polymer radical, TEMPO moiety on polystyrene is replaced to form the corresponding end‐functional polymers and block copolymers. The intermediates and final polymers are characterized by 1H NMR, UV, IR, and GPC measurements. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2387–2395