Biodegradable polymer blends of poly(lactic acid) and poly(ethylene glycol)

Sheth, Mihir; Kumar, Rajesh; Davé, Vipul; Gross, Richard A.; McCarthy, Stephen P.

doi:10.1002/(sici)1097-4628(19971121)66:8<1495::aid-app10>3.0.co;2-3

Cited by 426 publications

(347 citation statements)

References 4 publications

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“…As N C (and therefore the weight fraction of PEO) increases, T g decreases, consistent with continued dilution of mixed A/C domains by the low-T g component. The presence of only one T g in polymer blends is generally regarded as evidence for miscibility (41,42) and is consistent with the behavior of PLA and PEO homopolymers, which mix over wide ranges of molar masses and blend compositions (43,44). In the analogous LSL′ series, a single T g corresponding to the PLA block is observed that does not change as N A′ increases, because mixed domains inherently remain pure PLA (SI Appendix, Fig.…”

Section: Resultssupporting

confidence: 71%

Manipulating the ABCs of self-assembly via low-χ block polymer design

Chang

Bates

Lee

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Block polymer self-assembly typically translates molecular chain connectivity into mesoscale structure by exploiting incompatible blocks with large interaction parameters (χ ij ). In this article, we demonstrate that the converse approach, encoding low-χ interactions in ABC bottlebrush triblock terpolymers (χ AC ≲ 0), promotes organization into a unique mixed-domain lamellar morphology, which we designate LAM P . Transmission electron microscopy indicates that LAM P exhibits ACBC domain connectivity, in contrast to conventional three-domain lamellae (LAM 3 ) with ABCB periods. Complementary small-angle X-ray scattering experiments reveal a strongly decreasing domain spacing with increasing total molar mass. Self-consistent field theory reinforces these observations and predicts that LAM P is thermodynamically stable below a critical χ AC , above which LAM 3 emerges. Both experiments and theory expose close analogies to ABA′ triblock copolymer phase behavior, collectively suggesting that low-χ interactions between chemically similar or distinct blocks intimately influence self-assembly. These conclusions provide fresh opportunities for block polymer design with potential consequences spanning all self-assembling soft materials.block polymer | self-assembly | polymer nanostructure | domain spacing | LAM P B lock polymers are a diverse class of soft materials capable of self-assembling into complex periodic nanostructures. Synthetic command over composition, dispersity, sequence, and molecular architecture enables control over the mesoscopic order and macroscopic thermal, mechanical, rheological, and transport properties (1-4). The phase behavior of "simple" linear AB diblock copolymers is universally parameterized by the segregation strength χ AB N and relative volume fraction f, where χ AB represents the effective Flory-Huggins binary interaction parameter and N is the total volume-averaged degree of polymerization. Mixing behavior, captured through the mean-field concept of χ AB , is central to block polymer self-assembly: the competing demands of minimizing interfacial energy and maximizing configurational entropy only favor microphase separation when A-B interactions are repulsive (χ AB > 0) (5, 6). Extension to higher-order multiblock polymers introduces additional interaction parameters (χ ij ) that impact self-assembly and properties (7). For example, introducing a mutually incompatible C block (χ AC > 0, χ BC > 0) generates a host of new morphologies dictated by the chain connectivity (ABC, ACB, or BAC) and intrinsic χ ij -values (8, 9). In this rich phase space, designing multiblock polymers with a combination of miscible and immiscible blocks can also access new structures and impart useful functions (10, 11). Perhaps the best-known examples of such systems are linear ABA′ triblock copolymers (χ AB > 0, χ AA′ ≈ 0): their high-value industrial applications as thermoplastic elastomers are entirely enabled by A/A′ mixing and chain connectivity, which together create physically cross-linked materials with ex...

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Section: Resultssupporting

confidence: 71%

Manipulating the ABCs of self-assembly via low-χ block polymer design

Chang

Bates

Lee

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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“…It seems that counter-rotating twin screw extruders could find application for processing of selected biopolymers and biodegradable polymers characterized by low resistance to thermo-mechanical degradation. However, up to now information published in this field are very limited [26,27].…”

Section: Extruders As Chemical Reactors -Basic Conceptsmentioning

confidence: 99%

Reactive extrusion of bio-based polymer blends and composites – Current trends and future developments

Formela¹,

Zedler²,

Hejna³

et al. 2018

Express Polym. Lett.

109

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Abstract.Reactive extrusion is a cost-effective and environmentally-friendly method to produce new materials with enhanced performance properties. At present, reactive extrusion allows in-situ polymerization, modification/functionalization of polymers or chemical bonding of two (or more) immiscible phases, which can be carried out on commonly used extrusion lines. Although reactive extrusion has been known for many years, its application for processing of bio-based polymer blends and composites is a relatively new direction of scientific research. This work presents a literature review on recent advances in the processing of bio-based polymer blends and composites via reactive extrusion. We described compatibilization mechanisms for different types of biodegradable polymeric materials based on: (i) aliphatic polyesters, (ii) aliphatic polyesters/starch and (iii) aliphatic polyester/natural rubber systems. A special attention was focused on conventional and dynamic cross-linking of bio-based polymer blends and composites as an effective way to prepare new materials with unique properties e.g. biodegradable thermoplastic elastomers or shape-memory materials. Advantages and limitations affecting future trends in development of biodegradable polymer blends and composites reactive extrusion are also discussed.

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“…PEG with a value of M n 20 000 very effectively plasticized in a 40 % concentration of poly(L-lactic acid) (Kim et al, 2001). PEG in a concentration above 50 % possesses increased crystallinity, an increased module and decreased ductility (Sheth et al, 1997). Polypropylene glycol also exerts a plasticizing effect on poly(L-lactic acid), its effect on a decrease in crystallinity is lower than in PEG (Kulinski et al, 2006).…”

Section: Oligomeric and Polymeric Plasticizersmentioning

confidence: 99%