Synthesis and Characterization of Star Polymers and Cross-Linked Star Polymer Model Networks with Cores Based on an Asymmetric, Hydrolyzable Dimethacrylate Cross-Linker

Kafouris, Demetris; Themistou, Efrosyni; Patrickios, Costas S.

doi:10.1021/cm051604a

Cited by 44 publications

(41 citation statements)

References 26 publications

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“…The same concept is commonly used to study the structures of macromolecules and control the mechanical properties of synthetic polymer networks (29,32,(35)(36)(37)(38)(39). Consider a general end-linked network comprised of R-A 2 and R′-B f monomers where f represents the network branch functionality.…”

Section: Nds Conceptsmentioning

confidence: 99%

Counting primary loops in polymer gels

Zhou¹,

Woo²,

Cok³

et al. 2012

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

204

223

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Much of our fundamental knowledge related to polymer networks is built on an assumption of ideal end-linked network structure. Real networks invariably possess topological imperfections that negatively affect mechanical properties; modifications of classical network theories have been developed to account for these defects. Despite decades of effort, there are no known experimental protocols for precise quantification of even the simplest topological network imperfections: primary loops. Here we present a simple conceptual framework that enables primary loop quantification in polymeric materials. We apply this framework to measure the fraction of primary loop junctions in trifunctional PEG-based hydrogels. We anticipate that the concepts described here will open new avenues of theoretical and experimental research related to polymer network structure.responsive materials | topology | network disassembly spectrometry | tetrazine T he properties of all known polymer networks, from commodity materials like nylon, rubber, and plastics, to biological tissues such as the extracellular matrix (ECM) and cartilage, are defined by the network's chemical composition and structural topology (1-3). Much of our fundamental knowledge related to polymer materials, e.g., theories of elasticity and gelation, was built more than half a century ago upon an assumption of ideal end-linked network structure (Fig. 1A) (2, 4-7). Real networks invariably possess imperfections such as first-order elastically inactive dangling chains and primary loops (Fig. 1B), and higher-order elastic loop structures and chain entanglements; modifications of classical network theories have been developed to account for these defects (8-11).First-order network imperfections (Fig. 1B) have the most direct negative impact on the mechanical properties of materials. Dangling chains can be minimized if efficient end-linking reactions are used between functional groups present at 1:1 ratio. In contrast, kinetic constraints demand that primary loops exist regardless of functional group conversion (12). Unlike dangling chains, which can be readily quantified via titration or spectroscopy, there are no known methods for quantification of primary loops. Their prevalence is estimated from pregel measurements or variations between the properties of a given material and theoretical model networks (2,4,(7)(8)(9)(12)(13)(14)(15)(16)(17). These molecular-level mechanical imperfections could critically impact modern applications of polymer networks and gels (18-28), especially those built on an end-linked network architecture (29-33).Here we present a simple conceptual framework called network disassembly spectrometry (NDS) that enables facile, simultaneous quantification of the fraction of primary loops and the numbers and structures of dangling chains in end-linked materials via site-selective network disassembly. We apply this framework to degradable PEG hydrogels, which are similar to materials frequently used in tissue engineering applications (29,32).

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Section: Nds Conceptsmentioning

confidence: 99%

Counting primary loops in polymer gels

Zhou¹,

Woo²,

Cok³

et al. 2012

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

204

223

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“…In this approach, "in-out" star (co)polymers are first prepared in a three-step, one-pot procedure, involving sequential addition of monomer, cross-linker, and monomer again, whereas (co)network formation is accomplished in the fourth and final step via again adding the cross-linker. The resulting (co)networks bear both dangling and elastic polymer chains, with the former being formed upon the first polymerization of monomer (first addition step) and latter being formed upon the second polymerization of monomer (third addition step) (46)(47)(48)(49)(50). The two additions of the cross-linker give rise to two types of cores, the primary and the secondary, with the former being formed during the second addition step, and the latter during the fourth addition step.…”

Section: Star Polymersmentioning

confidence: 99%

Group Transfer Polymerization

Rikkou-Kalourkoti¹,

Webster²,

Patrickios³

2013

Encyclopedia of Polymer Science and Technology

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GROUP TRANSFER POLYMERIZATIONVol. 99 simplicity and robustness of controlled radical polymerizations in combination with the sensitivity of GTP to moisture and labile protons have restricted the employment of GTP for macromolecular engineering during the past 15 years. However, GTP is still attractive to several polymer synthesis research teams as it rapidly provides polymer products more homogeneous (Ð ∼1.2-1.3) than those of controlled radical polymerizations (Ð ∼1.2-1.6).The recent development of new superior catalysts for GTP provided new impetus for this polymerization method. The most noteworthy advancement was the demonstration by the groups of D. Taton (University of Bordeaux, France) and R. M. Waymouth (Stanford University, California) that NHCs equally and efficiently catalyze the GTP of acrylates, methacrylates, and acrylamides, and enable the synthesis of their block copolymers at any block sequence. Other important contributions have also been recently reported by the Groups of E. Y.-X. Chen (Colorado State University at Fort Collins, Colorado) and T. Kakuchi (Hokkaido University, Japan). Note, however, that GTP described in this article is not related to the rare earth metal-mediated group transfer polymerization developed by Yasuda in 1992 (23).This article is not intended to be a comprehensive review of GTP, but rather a brief update of an early review (24). For a complete account, the interested reader is referred to the various reviews published on the topic (25-27), and, in particular, the very recent one by Kakuchi and co-workers (28).

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“…An example of this is shown by the work of Patrickios and coworkers [47][48][49] who, in addition to synthesizing degradable ester-based cross-linkers, also utilized acid-labile siloxane and acetal groups to synthesize a dimethyldi(methacryloyloxy-1-ethoxy)silane (4) and di(methacryloyloxy-1-ethoxy)methane (5) cross-linker, respectively. These degradable cross-linkers were subsequently polymerized under group transfer polymerization conditions to yield CCS polymers with degradable cores.…”

Section: Degradable Cross-linkersmentioning

confidence: 99%

Recent Advances in Star Polymer Design: Degradability and the Potential for Drug Delivery

Wiltshire¹,

Qiao²

2007

Aust. J. Chem.

104

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The use of polymers as drug delivery devices represents an exciting area of development in the biomedical industry. This paper briefly highlights some of the different types of macromolecules that have attracted attention as potential drug delivery devices, with a particular focus on the class of star polymers known as core cross-linked star (CCS) polymers. The ability to control the rate at which encapsulated molecules can be released is an important factor in the design of efficient drug delivery devices. In this regard, several different techniques to incorporate degradable functionality into CCS polymers are examined as a potential means of controlling release kinetics.

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Synthesis and Characterization of Star Polymers and Cross-Linked Star Polymer Model Networks with Cores Based on an Asymmetric, Hydrolyzable Dimethacrylate Cross-Linker

Cited by 44 publications

References 26 publications

Counting primary loops in polymer gels

Counting primary loops in polymer gels

Group Transfer Polymerization

Recent Advances in Star Polymer Design: Degradability and the Potential for Drug Delivery

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