Superior sequence-controlled poly(L-lactide)-based bioplastic with tunable seawater biodegradation

Developing superior-performance marine-biodegradable plastics remains a critical challenge in mitigating marine plastic pollution. Commercially available biodegradable polymers, such as poly(L-lactide) (PLA), undergo slow degradation in complex marine environments. This study introduces an innovative bioplastic design that employs a facile ring-opening and coupling reaction to incorporate hydrophilic polyethylene glycol (PEG) into PLA, yielding PEG-PLA copolymers with either sequence-controlled alternating or random structures. These materials exhibit exceptional toughness in both wet and dry states, with an elongation at break of 1446.8% in the wet state. Specifically, PEG4kPLA2k copolymer biodegraded rapidly in proteinase K enzymatic solutions and had a significant weight loss of 71.5% after 28 d in seawater. The degradation primarily affects the PLA segments within the PEG-PLA copolymer, as evidenced by structural changes confirmed through comprehensive characterization techniques. The seawater biodegradability, in line with the Organization for Economic Cooperation and Development 306 Marine biodegradation test guideline, reached 72.63%, verified by quantitative biochemical oxygen demand analysis, demonstrating rapid chain scission in marine environments. The capacity of PEG-PLA bioplastic to withstand DI water and rapidly biodegrade in seawater makes it a promising candidate for preventing marine plastic pollution.

Crystallization and Morphology of Triple Crystalline Polyethylene-b-poly(ethylene oxide)-b-poly(ε-caprolactone) PE-b-PEO-b-PCL Triblock Terpolymers

The morphology and crystallization behavior of two triblock terpolymers of polymethylene, equivalent to polyethylene (PE), poly (ethylene oxide) (PEO), and poly (ε-caprolactone) (PCL) are studied: PE₂₂^7.1-b-PEO₄₆^15.1-b-PCL₃₂^10.4 (T1) and PE₃₇^9.5-b-PEO₃₄^8.8-b-PCL₂₉^7.6 (T2) (superscripts give number average molecular weights in kg/mol and subscripts composition in wt %). The three blocks are potentially crystallizable, and the triple crystalline nature of the samples is investigated. Polyhomologation (C1 polymerization), ring-opening polymerization, and catalyst-switch strategies were combined to synthesize the triblock terpolymers. In addition, the corresponding PE-b-PEO diblock copolymers and PE homopolymers were also analyzed. The crystallization sequence of the blocks was determined via three independent but complementary techniques: differential scanning calorimetry (DSC), in situ SAXS/WAXS (small angle X-ray scattering/wide angle X-ray scattering), and polarized light optical microscopy (PLOM). The two terpolymers (T1 and T2) are weakly phase segregated in the melt according to SAXS. DSC and WAXS results demonstrate that in both triblock terpolymers the crystallization process starts with the PE block, continues with the PCL block, and ends with the PEO block. Hence triple crystalline materials are obtained. The crystallization of the PCL and the PEO block is coincident (i.e., it overlaps); however, WAXS and PLOM experiments can identify both transitions. In addition, PLOM shows a spherulitic morphology for the PE homopolymer and the T1 precursor diblock copolymer, while the other systems appear as non-spherulitic or microspherulitic at the last stage of the crystallization process. The complicated crystallization of tricrystalline triblock terpolymers can only be fully grasped when DSC, WAXS, and PLOM experiments are combined. This knowledge is fundamental to tailor the properties of these complex but fascinating materials.

Sequential Crystallization and Multicrystalline Morphology in PE-b-PEO-b-PCL-b-PLLA Tetrablock Quarterpolymers

We investigate for the first time the morphology and crystallization of two novel tetrablock quarterpolymers of polyethylene (PE), poly(ethylene oxide) (PEO), poly(ε-caprolactone) (PCL), and poly(l-lactide) (PLLA) with four potentially crystallizable blocks: PE₁₈^7.1-b-PEO₃₇^15.1-b-PCL₂₆^10.4-b-PLLA₁₉^7.6 (Q1) and PE₂₉^9.5-b-PEO₂₆^8.8-b-PCL₂₃^7.6-b-PLLA₂₂^7.3 (Q2) (superscripts give number average molecular weights in kg/mol, and subscripts give the composition in wt %). Their synthesis was performed by a combination of polyhomologation (C1 polymerization) and ring-opening polymerization techniques using a ″catalyst-switch″ strategy, either ″organocatalyst/metal catalyst switch″ (Q1 sample, 96% isotactic tetrads) or ″organocatalyst/organocatalyst switch″ (Q2 sample, 84% isotactic tetrads). Their corresponding precursors—triblock terpolymers PE-b-PEO-b-PCL, diblock copolymers PE-b-PEO, and PE homopolymers—were also studied. Cooling and heating rates from the melt at 20 °C/min were employed for most experiments: differential scanning calorimetry (DSC), polarized light optical microscopy (PLOM), in situ small-angle X-ray scattering/wide-angle X-ray scattering (SAXS/WAXS), and atomic force microscopy (AFM). The direct comparison of the results obtained with these different techniques allows the precise identification of the crystallization sequence of the blocks upon cooling from the melt. SAXS indicated that Q1 is melt miscible, while Q2 is weakly segregated in the melt but breaks out during crystallization. According to WAXS and DSC results, the blocks follow a sequence as they crystallize: PLLA first, then PE, then PCL, and finally PEO in the case of the Q1 quarterpolymer; in Q2, the PLLA block is not able to crystallize due to its low isotacticity. Although the temperatures at which the PEO and PCL blocks and the PE and PLLA blocks crystallize overlap, the analysis of the intensity changes measured by WAXS and PLOM experiments allows identifying each of the crystallization processes. The quarterpolymer Q1 remarkably self-assembles during crystallization into tetracrystalline banded spherulites, where four types of different lamellae coexist. Nanostructural features arising upon sequential crystallization are found to have a relevant impact on the mechanical properties. Nanoindentation measurements show that storage modulus and hardness of the Q1 quarterpolymer significantly deviate from those of the stiff PE and PLLA blocks, approaching typical values of compliant PEO and PCL. Results are mainly attributed to the low crystallinity of the PE and PLLA blocks. Moreover, the Q2 copolymer exhibits inferior mechanical properties than Q1, and this can be related to the PE block within Q1 that has thinner crystal lamellae according to its much lower melting point.

Poly(ethylene oxide monomethyl ether)- block-poly(propylene succinate) Nanoparticles: Synthesis and Characterization, Enzymatic and Cellular Degradation, Micellar Solubilization of Paclitaxel, and in Vitro and in Vivo Evaluation

Polyester-based nanostructures are widely studied as drug-delivery systems due to their biocompatibility and biodegradability. They are already used in the clinic. In this work, we describe a new and simple biodegradable and biocompatible system as the Food and Drug Administration approved polyesters (poly-ε-caprolactone, polylactic acid, and poly(lactic- co-glycolic acid)) for the delivery of the anticancer drug paclitaxel (PTX) as a model drug. A hydrophobic polyester, poly(propylene succinate) (PPS), was prepared from a nontoxic alcohol (propylene glycol) and monomer from the Krebs's cycle (succinic acid) in two steps via esterification and melt polycondensation. Furthermore, their amphiphilic block copolyester, poly(ethylene oxide monomethyl ether)- block-poly(propylene succinate) (mPEO- b-PPS), was prepared by three steps via esterification followed by melt polycondensation and the addition of mPEO to the PPS macromolecules. Analysis of the in vitro cellular behavior of the prepared nanoparticle carriers (NPs) (enzymatic degradation, uptake, localization, and fluorescence resonance energy-transfer pair degradation studies) was performed by fluorescence studies. PTX was loaded to the NPs of variable sizes (30, 70, and 150 nm), and their in vitro release was evaluated in different cell models and compared with commercial PTX formulations. The mPEO- b-PPS copolymer analysis displays glass transition temperature < body temperature < melting temperature, lower toxicity (including the toxicity of their degradation products), drug solubilization efficacy, stability against spontaneous hydrolysis during transport in bloodstream, and simultaneous enzymatic degradability after uptake into the cells. The detailed cytotoxicity in vitro and in vivo tumor efficacy studies have shown the superior efficacy of the NPs compared with PTX and PTX commercial formulations.