ReviewSynthesis and characterization of poly(lactic acid) based graft copolymers
Introduction
Since the beginning of the concept of macromolecular chemistry, it has been the constant challenge for polymer scientists to search and find new monomer-to-polymer systems that may lead to the polymers with accurately prepared architectures, controlled molecular weights and promising properties. Suitably customized polymers are capable of spontaneous or stimuli-induced supramolecular self-assembly in aqueous media or at interfaces to yield micro or nano-structured entities with a virtually unlimited number of potential applications in pharmaceutics [1], medical diagnostics [2], personal care [3], and biotechnology [4].
Common practice of organic polymer chemists is to adapt the known organic reactions in such a way that compounds of low molecular weights are converted to polymers of high molecular weights. The same approach has been taken in living polymerization, which was first discovered by Szwarc for the polymerization of vinyl and diene monomers and published in Nature [5] and Journal of American Chemical Society [6]. Later on, in 1968, he published the monograph on living polymerization, which gives the most difficult fragments of kinetics and thermodynamics of polymerization [7]. This discovery led to develop the controlled cationic [8] and radical [9] vinyl polymerizations, closely related to the living anionic polymerizations as given by Szwarc [5], [6], [7]. Further, surface modification of polymers is of great interest in many fields, ranging, for example, from the protection of surfaces from corrosion to improving their biocompatibility [10].
Graft copolymerization is a well-known technique to impart a new property or enhance the existing properties in the parent polymer with minimum degradation of the original properties. The nature of the changes in the properties depends on the type of monomer being grafted, percentage of grafting, method of grafting, and distribution of the grafted chain throughout the parent polymer [11], [12]. McDowall and co-workers reported [12] that the high energy radiation induced pre-irradiation method showed higher elongation, recovery, and more uniform graft copolymer distribution throughout the cross section than the ceric ion-initiation method. Graft copolymers are finding their applications in development of selective permeable membranes [13] and outstanding sorption agents [14]. Graft copolymers have also been used as stabilizers between grafted and ungrafted polymers [15], [16].
Various extracellular matrix (ECM) proteins, such as collagen, fibronectin, and laminin, have been used as substrates for cell culture [17], [18], [19], [20]. However, they cannot be easily or reproducibly processed into three-dimensional scaffolds of good stability and mechanical properties. Thus, the use of polymeric materials as substrates has increased substantially in recent years because of their excellent mechanical properties and processability [21], [22]. Although bulk properties dictate the mechanical performance of biomaterials, cell and tissue-biomaterials interactions are surface phenomena and are governed by surface properties. Therefore, surface modification of polymer substrates is often required to improve their biocompatibility and also to allow the subsequent surface functionalization, such as enzyme and protein immobilization via covalent bonding [22], [23]. Thus, grafting provides a significant route to alter the physical and chemical properties of the polymer for specific end uses.
Section snippets
Scope
Advancements in grafting can be attributed to incredible efforts by a large number of investigators dedicated to the development of well-defined graft copolymers. It was documented that the development of a graft copolymer with a well-defined structure was essential nowadays, for application in different fields such as drug delivery, membranes for the separation of gases or liquids, hydrogels, thermoplastic elastomers, compatibilizers for polymer blends, polymeric emulsifiers, impact resistant
Polylactic acid (PLA)
Recently, interest in the synthesis of polymers with well-defined structure and macromolecular architecture has increased substantially [24]. Polymers with unique structures, such as block [25], [26], graft [27], [28], star [29], [30], gradient [31], hyper-branched [32], and comb [33], [34] structures, have found applications in colloids stabilization, crystal growth modification, induced micelle formation, and intelligent drug carrier systems [24], [35]. Polymers with unique architectures,
Polylactide graft copolymers
Recent years have indeed witnessed a growing interest in the investigation of the polylactic acid based graft copolymers for their applications in different fields. These graft copolymers have been analyzed critically by taking different monomers/polymers; such as chitosan, cellulose, starch, polyethylene glycol, vinyl based polymers, lignin, dextran, methyl methacrylate, maleic anhydride and graphene oxide.
PLA graft copolymer and its applications
Graft copolymers exhibit unique properties, which are generally not observed in their linear counterparts [191], [192]. The synthesis of graft copolymers has been achieved so far by three main methods: grafting-onto, in which side chains are first synthesized and then attached to a multifunctional linear backbone; [193] grafting-from, which involves the grafting of monomer from a linear macroinitiator; [194] and grafting-through (macromonomer method), in which the macromonomers are
Suggestions
Literature review on PLA grafting by various method has been carried out with a view to analyze the published data and to configure better operating conditions for the grafting of PLA with an aim to synthesize high molecular weight polymers with high yield. It has been observed from literature that ten parameters such as feed ratio, amount of catalyst, amount of co-catalyst, reaction time, reaction temperature, reaction pressure, PDI, Mw, types of monomer/polymer and types of catalyst affect
Concluding remarks
After reviewing the graft copolymers of PLA, it can be safely concluded that, production of ecofriendly high molecular weight biodegradable and biocompatible polymers with high yield can be achieved by adopting the routes of ring opening polymerization of lactide with monomers/polymers. Further, the production cost of different polymers depends upon the methods of grafting. As described above, great progress in the grafting of PLA has been achieved in the past few decades because they are very
Acknowledgment
Authors are thankful to Ravenshaw University, Cuttack, India and National Institute of Technology, Raipur, India. Financial support from the UGC (41-274/2012(SR)), New Delhi and CSIR (01(2572)EMR-II), New Delhi, India is greatly appreciated.
References (216)
- et al.
Lessons from nature: stimuli-responsive polymers and their biomedical applications
Trends Biotechnol.
(2002) - et al.
Polymer surface with graft chains
Prog. Polym. Sci.
(2003) - et al.
Synthesis and antitumor activity of α-1,4-polygalactosamine and N-acetyl-α-1,4-polygalactosamine immobilized 5-fluorouracils through hexamethylene spacer groups via urea, urea bonds
J. Control. Release
(1991) - et al.
Three-dimensional cultures of normal human osteoblasts: proliferation and differentiation potential in vitro and upon ectopic implantation in nude mice
Bone
(2002) - et al.
Laminin-rich extracellular matrix maintains high level of hepatocyte nuclear factor 4 in rat hepatocyte culture
Biochem. Biophys. Res. Commun.
(1995) - et al.
Plasma-induced graft polymerization of acrylic acid onto poly (ethylene terephthalate) films: characterization and human smooth muscle cell growth on grafted films
Biomaterials
(2002) - et al.
Poly (lactic acid) fiber: an overview
Prog. Polym. Sci.
(2007) - et al.
Melt–solid polycondensation of lactic acid and its biodegradability
Prog. Polym. Sci.
(2009) - et al.
Sterilization, toxicity, biocompatibility and clinical applications of polylactic acid/polyglycolic acid copolymers
Biomaterials
(1996) - et al.
Application of life cycle assessment to NatureWorksTM polylactide (PLA) production
Polym. Degrad. Stab.
(2003)
Late degradation tissue response to poly(l-lactide) bone plates and screws
Biomaterials
Surface modification of polymers: chemical, biological and surface analytical challenges
Biosens. Bioelectron.
The evolution of bone transplantation: molecular, cellular, and tissue strategies engineer human bone
Biomaterials
Biomimetic surface modification of poly (L-lactic acid) with chitosan and its effects on articular chondrocytes in vitro
Biomaterials
Immobilization of chitosan onto poly-l-lactic acid film surface by plasma graft polymerization to control the morphology of fibroblast
Biomaterials
Chondrocyte behaviours on poly-lactic acid (PLLA) membranes containing hydroxyl amide or carboxyl groups
Biomaterials
Preparation of uniform sized chitosan microspheres by membrane emulsification technique and application as a carrier of protein drug
J. Control. Release
Preparation of water-soluble chitosan/heparin complex and its application as wound healing accelerator
Biomaterials
Effect of lactic/glycolic acid side chains on the thermal degradation kinetics of chitosan derivatives
Polymer
Preparation of chitosan-g-polylactide graft copolymers via self-catalysis of phthaloylchitosan and their complexation with DNA
React. Funct. Polym.
Electrospun Chitosan-graft-PLGA nanofibres with significantly enhanced hydrophilicity and improved mechanical property
Colloids Surf. B: Biointerfaces
Synthesis and characterization of a novel amphiphilic chitosan–polylactide graft copolymer
Carbohydr. Polym.
Composites reinforced with cellulose based fibres
Prog. Polym. Sci.
Advances in cellulose ester performance and application
Prog. Polym. Sci.
‘Trends in polymer science’: a bright future for cellulose
Prog. Polym. Sci.
The plasticizer market: an assessment of traditional plasticizers and research trends to meet new challenges
Prog. Polym. Sci.
Towards an alternative compatibilizer for PLA/cellulose composites: grafting of xyloglucan with PLA
Carbohydr. Polym.
Synthesis of copoly(d, l-lactic acid) with relatively low molecular weight and in vitro degradation
Eur. Polym. J.
Biodegradable block copolymers as injectable drug delivery systems
Nature
Self-assembled amphiphilic hyaluronic acid graft Copolymers for targeted release of antitumoral drug
J. Drug Target.
The role of polymers in cosmetics
Recent Trends ACS Symposium Series
Living polymers
Nature
Polymerization Initiated by electron transfer to monomer. A new method of formation of block polymers
J. Am. Chem. Soc.
Carbanions Living Polymers and Electron Transfer Processes
Cationic Polymerization
Handbook of Radical Polymerization
γ‐Radiation-induced emulsion graft copolymerization of MMA onto jute fiber
Adv. Polym. Technol.
A comparison of the properties of ceric ion and preirradiated acrylic acid grafts to rayon fibers
Polym. J.
Preparation of cellulose derivatives containing the viologen moiety
J. Polym. Sci. Part C: Polym. Lett.
Graft copolymerization of methacrylate onto natural rubber: effect of polymerization conditions on particle morphology
J. Elastomers Plast.
Thermal decomposition of cellulose/synthetic polymer blends containing grafted products. III. Cellulose' poly (methyl methacrylate) blends
Polym. J.
Fibronectin combined with stem cell factor plays an important role in melanocyte proliferation, differentiation and migration in cultured mouse neural crest cells
Pigment Cell Res.
Hepatocyte function and extracellular matrix geometry: long-term culture in a sandwich configuration
FASEB J.
Surface modification of polymers for medical applications
Biomaterials
Grafting of Polymer Surfaces. In Encyclopedia of Surface and Colloid Science
Design and synthesis of different types of poly (lactic acid)
Polym. Sci. Technol. Gen.
Living radical polymerization of alkyl methacrylates and synthesis of their block copolymers
Macromolecules
Preparation of block copolymers of polystyrene and poly (t-butyl acrylate) of various molecular weights and architectures by atom transfer radical polymerization
J. Polym. Sci. A Polym. Chem.
Copolymerization of n-butyl acrylate with methyl methacrylate and PMMA macromonomers: comparison of reactivity ratios in conventional and atom transfer radical copolymerization
Macromolecules
Unimolecular combination of an atom transfer radical polymerization initiator and a lactone monomer as a route to new graft copolymers
Macromolecules
Cited by (105)
Simulated gastrointestinal digestion of polylactic acid (PLA) biodegradable microplastics and their interaction with the gut microbiota
2023, Science of the Total EnvironmentEnhancement in thermal stability and mechanical performance of modified polyketone/aramid short fiber composites with controlled interface
2023, Composites Part A: Applied Science and ManufacturingFabrication of innocuous hydrogel scaffolds based on modified dextran for biotissues
2022, Carbohydrate Research