Anomalous increase in modulus upon hydration in random copolymers with hydrophobic segments and hydrophilic blocks

Bédoui, Fahmi; Widjaja, Leonardus Kresna; Luk, Arnold; Bolikal, Durgadas; Murthy, N. Sanjeeva; Kohn, Joachim

doi:10.1039/c1sm06619f

Cited by 20 publications

(28 citation statements)

References 40 publications

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“…This is also consistent with the glass transition temperature ( T g ) measurements (wet T g = 64°C for PDTEC and 113°C for PI 2 DTEC) which indicate the PI 2 DTEC is more rigid than PDTEC. 13 …”

Section: Resultsmentioning

confidence: 99%

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Structure of Biodegradable Films at Aqueous Surfaces: X-ray Diffraction and Spectroscopy Studies of Polylactides and Tyrosine-Derived Polycarbonates

et al. 2013

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Three representative polymers of increasing modulus, poly(D,L-lactic acid), PDLLA, poly(desaminotyrosyl-tyrosine ethyl ester carbonate), PDTEC, and the same polymer with iodinated DTE segments, PI2DTEC, were characterized by surface-pressure versus area (Π-A) isotherms and surface sensitive X-ray diffraction techniques. 10–100 Å thick films were prepared for these studies by spreading dilute polymer solutions at air-water interfaces. The general properties of the isotherms and the Flory exponents, determined from the isotherms, vary in accordance with the increasing modulus of PDLLA, PDTEC, PI2DTEC, respectively. The analysis of in-situ X-ray reflectivity and grazing incidence X-ray diffraction (GIXD) measurements from films at aqueous surfaces provides a morphological picture that is consistent with the modulus of the polymers, and to a large extent, with their packing in their dry-bulk state. Large absorption of X-rays by iodine enabled X-ray spectroscopic studies under near-total-reflection conditions to determine the iodine distribution in the PI2DTEC film and complement the structural model derived from reflectivity and GIXD. These structural studies lay the foundation for future studies of polymer-protein interactions at aqueous interfaces.

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Section: Resultsmentioning

confidence: 99%

“…Wet moduli of PDLLA (unpublished, Murthy et al, 2012), PDTEC and PI 2 DTEC 13 are 1.3, 1.47, and 2.19 GPa, respectively. Two of the polymers are tyrosine-derived polycarbonates (Tyr-PCs), 14,15 made of desaminotyrosyl-tyrosine ethyl ester (DTE) and iodinated DTE segments.…”

Section: Introductionmentioning

confidence: 93%

Structure of Biodegradable Films at Aqueous Surfaces: X-ray Diffraction and Spectroscopy Studies of Polylactides and Tyrosine-Derived Polycarbonates

et al. 2013

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“…One hypothesis explaining this phenomena is that hydration-induced phase segregation in the amphiphilic network results in a change in load transfer within the polymer. 70,72 Another competing hypothesis is that the swelling of the hydrophilic (PEG) domains stiffens the polymer. 71 For tissue engineering applications, hydration-induced stiffening may be exploited to engineer amphiphilic scaffolds with self-fixation behaviors.…”

Section: Physical Propertiesmentioning

confidence: 99%

Biodegradable PEG-Based Amphiphilic Block Copolymers for Tissue Engineering Applications

Kutikov

Song

2015

ACS Biomater. Sci. Eng.

155

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Biodegradable tissue engineering scaffolds have great potential for delivering cells/therapeutics and supporting tissue formation. Polyesters, the most extensively investigated biodegradable synthetic polymers, are not ideally suited for diverse tissue engineering applications due to limitations associated with their hydrophobicity. This review discusses the design and applications of amphiphilic block copolymer scaffolds integrating hydrophilic poly(ethylene glycol) (PEG) blocks with hydrophobic polyesters. Specifically, we highlight how the addition of PEG results in striking changes to the physical properties (swelling, degradation, mechanical, handling) and biological performance (protein & cell adhesion) of the degradable synthetic scaffolds in vitro. We then perform a critical review of how these in vitro characteristics translate to the performance of biodegradable amphiphilic block copolymer-based scaffolds in the repair of a variety of tissues in vivo including bone, cartilage, skin, and spinal cord/nerve. We conclude the review with recommendations for future optimizations in amphiphilic block copolymer design and the need for better-controlled in vivo studies to reveal the true benefits of the amphiphilic synthetic tissue scaffolds.

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“…The wet modulus is higher than the dry modulus in iodinated polymers with 45 to 60 vol% PEG [34] and protein-repulsive effect of PEG is negated by the presence of iodine in these polymers [35]. The known effects of iodine (it makes the polymer hydrophobic and increases the T g , Table 1) do not explain these observations.…”

Section: Resultsmentioning

confidence: 99%

“…At low PEG concentration (<13 wt%), water makes the polymer soft, and at significantly higher PEG contents (>40 wt%), the hydrated material behaves like a gel [15]. Between these two extremes, water has been shown to increase the modulus of the polymer [34]. SANS data show between water content of 13 to 24 wt %, PEG segments phase separate to form hydrated domains.…”

Section: Resultsmentioning

confidence: 99%

Study of nanoscale structures in hydrated biomaterials using small-angle neutron scattering

Luk¹,

Murthy²,

Wang³

et al. 2012

Acta Biomaterialia

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Distribution of water in three classes of biomedically relevant and degradable polymers was investigated using small-angle neutron scattering. In semicrystalline polymers, such as poly(lactic acid) and poly(glycolic acid), water was found to diffuse preferentially into the noncrystalline regions. In amorphous polymers, such as poly(D,L-lactic acid) and poly(lactic-co-glycolic acid), the scattering after 7-days of incubation was attributed to water in microvoids that form following the hydrolytic degradation of the polymer. In amorphous copolymers containing hydrophobic segments (desaminotyrosyl-tyrosine ethyl ester) and hydrophilic blocks (poly(ethylene glycol) PEG), a sequence of distinct regimes of hydration were observed: homogeneous distribution (~ 10 Å length scales) at <13 wt% PEG (~ 1 water per EG), clusters of hydrated domains (~50 Å radius) separated at 24 wt% PEG (1 to 2 water per EG), uniformly distributed hydrated domains at 41 wt% PEG (~ 4 water per EG), and phase inversion at > 50 wt% PEG ( > 6 water per EG ). Increasing PEG content increased the number of these domains with only a small decrease in distance between the domains. These discrete domains appeared to coalesce to form submicron droplets at ~60 °C, above the melting temperature of crystalline PEG. Significance of such observations on the evolution of μm size channels that form during hydrolytic erosion is discussed.

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Anomalous increase in modulus upon hydration in random copolymers with hydrophobic segments and hydrophilic blocks

Cited by 20 publications

References 40 publications

Structure of Biodegradable Films at Aqueous Surfaces: X-ray Diffraction and Spectroscopy Studies of Polylactides and Tyrosine-Derived Polycarbonates

Structure of Biodegradable Films at Aqueous Surfaces: X-ray Diffraction and Spectroscopy Studies of Polylactides and Tyrosine-Derived Polycarbonates

Biodegradable PEG-Based Amphiphilic Block Copolymers for Tissue Engineering Applications

Study of nanoscale structures in hydrated biomaterials using small-angle neutron scattering

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