Biocompatible hyperbranched polyurethane/multi-walled carbon nanotube composites as shape memory materials

Deka, Harekrishna; Karak, Niranjan; Kalita, Ranjan; Buragohain, Alak Kumar

doi:10.1016/j.carbon.2010.02.009

Cited by 127 publications

(92 citation statements)

References 35 publications

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“…In both the cases, the crystal structure of PCL remained intact. However, the increase in intensity of the peaks corresponding to PCL crystal in Messua ferrea oil-based hyperbranched polyurethane/MWCNT nanocomposites is also observed (59). The d-spacing and approximate size of the nanomaterials can also be determined by Bragg's equation and Scherrer's equation (in case of homogeneous strain systems), respectively, as given below:…”

Section: X-ray Diffraction Studymentioning

confidence: 93%

“…are included in such applications. Bio-based hyperbranched polyurethanes and their nanocomposites exhibited excellent shape memory property (44,45,(51)(52)(53)(54)59,62,68,77,78,(83)(84)(85). The incorporation of different nanomaterials on such nanocomposites showed improved shape memory behaviors from their respective pristine polyurethanes.…”

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confidence: 93%

“…However, the speed of recovery, that is the rate of recovery from a fixed temporary shape to its original shape during the recovery process of such materials under the application of an appropriate stimulus, is also important for its applications. The formation of suitable nanocomposites influences all these properties of bio-based shape memory polyurethanes (44,57,59,62,67,68). The incorporation of appropriate nanomaterial in the matrix enhances the shape memory behaviors of the bio-based polyurethane (Fig.…”

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confidence: 98%

“…The glass transition temperature (T g ), melting temperature (T m ), crystallinity, kinetics of reaction, amount of endothermic or exothermic energy, etc. can be studied by DSC (59,67,72). It reveals the mobility of molecular chains with variation of thermal energy.…”

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confidence: 99%

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Bio‐Based Hyperbranched Polyurethane Nanocomposites

Karak

2015

Encyclopedia of Polymer Science and Technology

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BIO-BASED HYPERBRANCHED POLYURETHANE NANOCOMPOSITESadjusting the ratio of isocyanate (-NCO) to hydroxyl (-OH) functionality and the chemical composition in the final structure of the polyurethane, different types of polymeric products like thermosetting resin and elastomer as well as thermoplastic and fiber can be obtained (3). In all such polyurethanes, the main linkage, urethane (-NH-C(=O) -O-) is a unique combination of rigid amide (-NH-C=O), which has a tendency to donate proton, and a flexible ester (-O-C=O) group, which has a tendency to accept proton. Further flexibility arises from the flexible soft segment and long hydrocarbon part of fatty acid chains of the vegetable oil component present in the bio-based segmented polyurethanes. Moreover, they are biodegradable and biocompatible. All these unique features of bio-based polyurethanes widen their applications in the domains of coating, paint, adhesive, sealant, composite, biomaterial, smart material, and so on.Again, incorporation of branching in the polymer structure greatly influences the processing and properties of the branched polymer. Thus hyperbranched polymers are treated as macromolecules for 21st century. These hyperbranched polymers are one type of dendritic polymers ( Fig. 1), where the other type is a perfectly regular structure with a three-dimensional architecture, known as a dendrimer (4). However, hyperbranched polymers are preferred in most of the industrial applications over multistep laborious synthesized dendrimers because of easier and simpler one-step synthetic protocol of the former as they can accommodate some defects in their structures. Thus mass-scale industrial production at relatively low cost is possible for hyperbranched polymers like conventional linear polymers. However, hyperbranched polymers enjoy many advantages over linear polymers (Fig. 1). These include a unique three-dimensional structural architecture with dendritic, linear, and terminal units, the presence of a large number of freely exposed surface groups, low polydispersity index, low viscosity, high solubility, high compatibility with other materials, etc. Therefore, bio-based hyperbranched polyurethanes are preferred as superior materials over their conventional analogs for different advanced applications.However, "virginity is not a virtue" in case of polymer, whatsoever the structural architecture is! Thus bio-based hyperbranched polyurethanes also require to be adulterated by incorporation of appropriate additives or ingredients. It is pertinent to mention here that most of the vegetable oil-based hyperbranched polyurethanes do not have required mechanical strength and toughness, although they possess very good flexibility. In this vein, conventional filled and composite systems are widely used, although both the approaches suffer from serious drawbacks, as a huge amount of additive(s) is necessary to be incorporated to achieve the desired level of performance of the stated polyurethanes. Most importantly, the resultant products lost most of the central a...

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Section: X-ray Diffraction Studymentioning

confidence: 93%

mentioning

confidence: 93%

mentioning

confidence: 98%

mentioning

confidence: 99%

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Bio‐Based Hyperbranched Polyurethane Nanocomposites

Karak

2015

Encyclopedia of Polymer Science and Technology

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“…In comparison with neat Morthane, polymer carbon nanotube composites containing 2.9 vol% (5 wt%) MWCNTs exhibited improved shape fixity ratios (from 56 to 70% for ε m = 250%) and increased recovery stresses from 0.6 MPa to 1.4 MPa, when passing the soft segmental melting transition. Deka et al [197] studied Mesua ferrea L. seed oil-based, epoxy-modified hyperbranched PU composites with MWCNTs. The composites with 5, 10 and 20 wt% of epoxy resin revealed shape retentions between 74 and 87%, shape recoverabilities of 90 to 98% and significantly improved tensile strengths towards pristine hyperbranched PU.…”

Section: Review Of Progressmentioning

confidence: 99%

Review on the Functional Determinants and Durability of Shape Memory Polymers

Pretsch

2010

Polymers

110

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Shape memory polymers (SMP) belong to the class of stimuli-responsive materials and have generated significant research interest. Their capability to retain an imposed, temporary shape and to recover the initial, permanent shape upon exposure to an external stimulus depends on the "functional determinants", which in simplistic terms, can be divided into structural/morphological and processing/environmental factors. The primary aim of the first part of this review is to reflect the knowledge about these fundamental relationships. In a next step, recent advances in shape memory polymer composites are summarized. In contrast to earlier reviews, studies on the impairment of shape memory properties through various factors, such as aging, compression and hibernation, lubricants, UV light and thermo-mechanical cycling, are extensively reviewed. Apart from summarizing the state-of-the-art in SMP research, recent progress is commented.

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