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Biodegradable and Bio-Based Polymers

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A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (29 February 2016) | Viewed by 134312

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Dr. Guozhan Jiang

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School of Biology, Chemistry and Forensic Science, Faculty of Science and Engineering, University of Wolverhampton, Wulfruna Street, Wolverhampton WV1 1SB, UK

Prof. Dr. Marek M. Kowalczuk

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1. Wolverhampton School of Biology, Chemistry and Forensic Science, Faculty of Science and Engineering, University of Wolverhampton, Wolverhampton WV1 1LY, UK
2. Centre of Polymer and Carbon Materials, Polish Academy of Sciences, 41-800 Zabrze, Poland
Interests: biocompatible and biodegradable polymer systems; polymer mass spectrometry; bioactive oligomers; controlled drug delivery systems; ring-opening polymerization; forensic engineering of advanced polymeric materials
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Dear Colleagues,

Biodegradable polymers could be manufactured from renewable or fossil sources. On the other hand, the bio-based polymers could be either biodegradable or non-biodegradable. The use of non-biodegradable polymeric materials in daily life has increased dramatically in recent decades. Hence, there is a need of balancing the social, economic, and environmental aspects aimed at their further development in terms of the world economy. After disposal, a high level of plastic debris persists in the environment and generates several cumulative effects. Biodegradable polymer technologies are becoming particularly significant as a potential solution for waste management. Sugar-based macromolecules and aliphatic polyesters with biodegradable properties are some of the more important materials, which are synthesized using enzymatic and chemical methods. New opportunities for specific applications are related with the introduction of stimuli-responsive or bioactive properties to the biodegradable polymers. Evaluation of the relationships between structure, properties, and behavior, before, during, and after practical applications are needed in order to define and minimize the potential failure of novel biodegradable polymer products. Due to the wide range of their potential uses (e.g., in the field of medicine, compostable polymer packages, especially for long-shelf life products, such as cosmetics or household chemicals, as well as in agrochemical formulations) testing in simulated environments is needed before they are rolled out. Such an approach will help to design novel functional plastic materials and to avoid the failure of the commercial products manufactured from them.

In this Special Issue, we aim to present a contemporary overview of recent developments in the field of biodegradable and bio-based polymers. Reviews, full papers, and short communications, covering the aspects of the current trends in expansion of such polymeric materials are all welcome.

Prof. Dr. Marek M. Kowalczuk
Dr. Guozhan Jiang
Guest Editors

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Keywords

synthesis of biodegradable and bio-based polymers
structure-property relationships of biodegradable and bio-based polymers
novel analytical approaches in characterization of biodegradable and bio-based polymers
chemical modification of biodegradable and bio-based polymers
testing of biodegradable and bio-based polymeric materials
commercial applications of biodegradable and bio-based polymers

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Published Papers (14 papers)

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13 pages, 3223 KiB

Open AccessFeature PaperCommunication

Biomineralization of Engineered Spider Silk Protein-Based Composite Materials for Bone Tissue Engineering

by John G. Hardy, Jose Guillermo Torres-Rendon, Aldo Leal-Egaña, Andreas Walther, Helmut Schlaad, Helmut Cölfen and Thomas R. Scheibel

Materials 2016, 9(7), 560; https://doi.org/10.3390/ma9070560 - 11 Jul 2016

Cited by 33 | Viewed by 9158

Abstract

Materials based on biodegradable polyesters, such as poly(butylene terephthalate) (PBT) or poly(butylene terephthalate-co-poly(alkylene glycol) terephthalate) (PBTAT), have potential application as pro-regenerative scaffolds for bone tissue engineering. Herein, the preparation of films composed of PBT or PBTAT and an engineered spider silk protein, (eADF4(C16)), that displays multiple carboxylic acid moieties capable of binding calcium ions and facilitating their biomineralization with calcium carbonate or calcium phosphate is reported. Human mesenchymal stem cells cultured on films mineralized with calcium phosphate show enhanced levels of alkaline phosphatase activity suggesting that such composites have potential use for bone tissue engineering. Full article

(This article belongs to the Special Issue Biodegradable and Bio-Based Polymers)

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15 pages, 2389 KiB

Open AccessArticle

Recyclability of PET/WPI/PE Multilayer Films by Removal of Whey Protein Isolate-Based Coatings with Enzymatic Detergents

by Patrizia Cinelli, Markus Schmid, Elodie Bugnicourt, Maria Beatrice Coltelli and Andrea Lazzeri

Materials 2016, 9(6), 473; https://doi.org/10.3390/ma9060473 - 14 Jun 2016

Cited by 32 | Viewed by 11751

Abstract

Multilayer plastic films provide a range of properties, which cannot be obtained from monolayer films but, at present, their recyclability is an open issue and should be improved. Research to date has shown the possibility of using whey protein as a layer material with the property of acting as an excellent barrier against oxygen and moisture, replacing petrochemical non-recyclable materials. The innovative approach of the present research was to achieve the recyclability of the substrate films by separating them, with a simple process compatible with industrial procedures, in order to promote recycling processes leading to obtain high value products that will beneficially impact the packaging and food industries. Hence, polyethyleneterephthalate (PET)/polyethylene (PE) multi-layer film was prepared based on PET coated with a whey protein layer, and then the previous structure was laminated with PE. Whey proteins, constituting the coating, can be degraded by enzymes so that the coating films can be washed off from the plastic substrate layer. Enzyme types, dosage, time, and temperature optima, which are compatible with procedures adopted in industrial waste recycling, were determined for a highly-efficient process. The washing of samples based on PET/whey and PET/whey/PE were efficient when performed with enzymatic detergent containing protease enzymes, as an alternative to conventional detergents used in recycling facilities. Different types of enzymatic detergents tested presented positive results in removing the protein layer from the PET substrate and from the PET/whey/PE multilayer films at room temperature. These results attested to the possibility of organizing the pre-treatment of the whey-based multilayer film by washing with different available commercial enzymatic detergents in order to separate PET and PE, thus allowing a better recycling of the two different polymers. Mechanical properties of the plastic substrate, such as stress at yield, stress and elongation at break, evaluated by tensile testing on films before and after cleaning, were are not significantly affected by washing with enzymatic detergents. Full article

(This article belongs to the Special Issue Biodegradable and Bio-Based Polymers)

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12 pages, 3420 KiB

Open AccessArticle

Room Temperature Consolidation of a Porous Poly(lactic-co-glycolic acid) Matrix by the Addition of Maltose to the Water-in-Oil Emulsion

by Eliana Esposito, Flavia Ruggiero, Raffaele Vecchione and Paolo Antonio Netti

Materials 2016, 9(6), 420; https://doi.org/10.3390/ma9060420 - 27 May 2016

Cited by 5 | Viewed by 5620

Abstract

In composite materials made of polymer matrices and micro-nano dispersed compartments, the morphology of the dispersed phase can strongly affect several features of the final material, including stability, loading efficiency, and kinetic release of the embedded molecules. Such a polymer matrix composite can be obtained through the consolidation of the continuous polymer phase of a water-in-oil (W/O) emulsion. Here, we show that the morphology of the dispersed phase in a poly(lactic-co-glycolic acid, PLGA) matrix can be optimized by combining an effective mild temperature drying process with the addition of maltose as a densifying compound for the water phase of the emulsion. The influence of this addition on final stability and consequent optimal pore distribution was theoretically and experimentally confirmed. Samples were analyzed in terms of morphology on dried flat substrates and in terms of rheology and interfacial tension at the liquid state. While an increase of interfacial tension was found following the addition of maltose, the lower difference in density between the two emulsion phases coming from the addition of maltose allowed us to estimate a reduced creaming tendency confirmed by the experimental observations. Rheological measurements also confirmed an improved elastic behavior for the maltose-containing emulsion. Full article

(This article belongs to the Special Issue Biodegradable and Bio-Based Polymers)

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16 pages, 1777 KiB

Open AccessArticle

Oxidized Polyethylene Wax as a Potential Carbon Source for PHA Production

by Iza Radecka, Victor Irorere, Guozhan Jiang, David Hill, Craig Williams, Grazyna Adamus, Michal Kwiecień, Adam A. Marek, Jan Zawadiak, Brian Johnston and Marek Kowalczuk

Materials 2016, 9(5), 367; https://doi.org/10.3390/ma9050367 - 13 May 2016

Cited by 57 | Viewed by 11796

Abstract

We report on the ability of bacteria to produce biodegradable polyhydroxyalkanoates (PHA) using oxidized polyethylene wax (O-PEW) as a novel carbon source. The O-PEW was obtained in a process that used air or oxygen as an oxidizing agent. R. eutropha H16 was grown for 48 h in either tryptone soya broth (TSB) or basal salts medium (BSM) supplemented with O-PEW and monitored by viable counting. Study revealed that biomass and PHA production was higher in TSB supplemented with O-PEW compared with TSB only. The biopolymers obtained were preliminary characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The detailed structural evaluation at the molecular level was performed by electrospray ionization tandem mass spectrometry (ESI-MS/MS). The study revealed that, when TSB was supplemented with O-PEW, bacteria produced PHA which contained 3-hydroxybutyrate and up to 3 mol % of 3-hydroxyvalerate and 3-hydroxyhexanoate co-monomeric units. The ESI-MS/MS enabled the PHA characterization when the content of 3-hydroxybutyrate was high and the appearance of other PHA repeating units was very low. Full article

(This article belongs to the Special Issue Biodegradable and Bio-Based Polymers)

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11 pages, 10391 KiB

Open AccessArticle

Biopolymer Green Lubricant for Sustainable Manufacturing

by Shih-Chen Shi and Fu-I Lu

Materials 2016, 9(5), 338; https://doi.org/10.3390/ma9050338 - 5 May 2016

Cited by 32 | Viewed by 5667

Abstract

We report on the preparation of a biopolymer thin film by hydroxypropyl methylcellulose (HPMC), which can be used as a dry green lubricant in sustainable manufacturing. The thin films were characterized through scanning electron microscopy, energy-dispersive spectroscopy, and Raman spectroscopy; the films showed desirable levels of thickness, controllability, and uniformity. Tribology tests also showed desirable tribological and antiwear behaviors, caused by the formation of transfer layers. Zebrafish embryo toxicity studies showed that HPMC has excellent solubility and biocompatibility, which may show outstanding potential for applications as a green lubricant. The results of the present study show that these techniques for biopolymer HPMC provide an ecologically responsible and convenient method for preparing functional thin films, which is particularly applicable to sustainable manufacturing. Full article

(This article belongs to the Special Issue Biodegradable and Bio-Based Polymers)

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15 pages, 4231 KiB

Open AccessFeature PaperArticle

Poly(lactide)-g-poly(butylene succinate-co-adipate) with High Crystallization Capacity and Migration Resistance

by Xi Yang, Huan Xu, Karin Odelius and Minna Hakkarainen

Materials 2016, 9(5), 313; https://doi.org/10.3390/ma9050313 - 27 Apr 2016

Cited by 30 | Viewed by 7226

Abstract

Plasticized polylactide (PLA) with increased crystallization ability and prolonged life-span in practical applications due to the minimal plasticizer migration was prepared. Branched plasticized PLA was successfully obtained by coupling poly(butylene succinate-co-adipate) (PBSA) to crotonic acid (CA) functionalized PLA. The plasticization behavior of PBSA coupled PLA (PLA-CA-PBSA) and its counterpart PBSA blended PLA (PLA/PBSA) were fully elucidated. For both PLA-CA-PBSA and PLA/PBSA, a decrease of T_g to around room temperature and an increase in the elongation at break of PLA from 14% to 165% and 460%, respectively, were determined. The crystallinity was increased from 2.1% to 8.4% for PLA/PBSA and even more, to 10.6%, for PLA-CA-PBSA. Due to the inherent poor miscibility between the PBSA and PLA, phase separation occurred in the blend, while PLA-CA-PBSA showed no phase separation which, together with the higher crystallinity, led to better oxygen barrier properties compared to neat PLA and PLA/PBSA. A higher resistance to migration during hydrolytic degradation for the PLA-CA-PBSA compared to the PLA/PBSA indicated that the plasticization effect of PBSA in the coupled material would be retained for a longer time period. Full article

(This article belongs to the Special Issue Biodegradable and Bio-Based Polymers)

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13 pages, 4114 KiB

Open AccessFeature PaperArticle

Synthesis and Structural Characterization of Bioactive PHA and γ-PGA Oligomers for Potential Applications as a Delivery System

by Iwona Kwiecień, Iza Radecka, Michał Kwiecień and Grażyna Adamus

Materials 2016, 9(5), 307; https://doi.org/10.3390/ma9050307 - 25 Apr 2016

Cited by 14 | Viewed by 6257

Abstract

The (trans)esterification reaction of bacterial biopolymers with a selected bioactive compound with a hydroxyl group was applied as a convenient method for obtaining conjugates of such compound. Tyrosol, a naturally occurring phenolic compound, was selected as a model of a bioactive compound with a hydroxyl group. Selected biodegradable polyester and polyamide, poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) and poly-γ-glutamic acid (γ-PGA), respectively, were used. The (trans)esterification reactions were carried out in melt mediated by 4-toluenesulfonic acid monohydrate. The structures of (trans)esterification products were established at the molecular level with the aid of ESI-MS² (electrospray ionization tandem mass spectrometry) and/or ¹H NMR (nuclear magnetic resonance) techniques. Performed analyses confirmed that the developed method leads to the formation of conjugates in which bioactive compounds are covalently bonded to biopolymer chains. The amount of covalently bonded bioactive compounds in the resulting conjugates depends on the type of biopolymers applied in synthesis. Full article

(This article belongs to the Special Issue Biodegradable and Bio-Based Polymers)

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15 pages, 3737 KiB

Open AccessArticle

Synthesis of Dendronized Poly(l-Glutamate) via Azide-Alkyne Click Chemistry

by Peter Perdih, Andrej Kržan and Ema Žagar

Materials 2016, 9(4), 242; https://doi.org/10.3390/ma9040242 - 29 Mar 2016

Cited by 4 | Viewed by 8194

Abstract

Poly(l-glutamate) (PGlu) was modified with a second-generation dendron to obtain the dendronized polyglutamate, P(Glu-D). Synthesized P(Glu-D) exhibited a degree of polymerization (DP_n) of 46 and a 43% degree of dendronization. Perfect agreement was found between the P(Glu-D) expected structure and the results of nuclear magnetic resonance spectroscopy (NMR) and size-exclusion chromatography coupled to a multi-angle light-scattering detector (SEC-MALS) analysis. The PGlu precursor was modified by coupling with a bifunctional building block (N₃-Pr-NH₂) in the presence of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM) coupling reagent. The second-generation polyamide dendron was prepared by a stepwise procedure involving the coupling of propargylamine to the l-lysine carboxyl group, followed by attaching the protected 2,2-bis(methylol)propionic acid (bis-MPA) building block to the l-lysine amino groups. The hydroxyl groups of the resulting second-generation dendron were quantitatively deprotected under mild acidic conditions. The deprotected dendron with an acetylene focal group was coupled to the pendant azide groups of the modified linear copolypeptide, P(Glu-N₃), in a Cu(I) catalyzed azide-alkyne cycloaddition reaction to form a 1,4-disubstituted triazole. The dendronization reaction proceeded quantitatively in 48 hours in aqueous medium as confirmed by ¹H NMR and Fourier transform infrared spectroscopy (FT-IR) spectroscopy. Full article

(This article belongs to the Special Issue Biodegradable and Bio-Based Polymers)

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15 pages, 5030 KiB

Open AccessArticle

A Novel HA/β-TCP-Collagen Composite Enhanced New Bone Formation for Dental Extraction Socket Preservation in Beagle Dogs

by Ko-Ning Ho, Eisner Salamanca, Kuo-Chi Chang, Tsai-Chin Shih, Yu-Chi Chang, Haw-Ming Huang, Nai-Chia Teng, Che-Tong Lin, Sheng-Wei Feng and Wei-Jen Chang

Materials 2016, 9(3), 191; https://doi.org/10.3390/ma9030191 - 11 Mar 2016

Cited by 19 | Viewed by 8245

Abstract

Past studies in humans have demonstrated horizontal and vertical bone loss after six months following tooth extraction. Many biomaterials have been developed to preserve bone volume after tooth extraction. Type I collagen serves as an excellent delivery system for growth factors and promotes angiogenesis. Calcium phosphate ceramics have also been investigated because their mineral chemistry resembles human bone. The aim of this study was to compare the performance of a novel bioresorbable purified fibrillar collagen and hydroxyapatite/β-tricalcium phosphate (HA/β-TCP) ceramic composite versus collagen alone and a bovine xenograft-collagen composite in beagles. Collagen plugs, bovine graft-collagen composite and HA/β-TCP-collagen composite were implanted into the left and right first, second and third mandibular premolars, and the fourth molar was left empty for natural healing. In total, 20 male beagle dogs were used, and quantitative and histological analyses of the extraction ridge was done. The smallest width reduction was 19.09% ± 8.81% with the HA/β-TCP-collagen composite at Week 8, accompanied by new bone formation at Weeks 4 and 8. The HA/β-TCP-collagen composite performed well, as a new osteoconductive and biomimetic composite biomaterial, for socket bone preservation after tooth extraction. Full article

(This article belongs to the Special Issue Biodegradable and Bio-Based Polymers)

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17 pages, 8616 KiB

Open AccessFeature PaperArticle

Influence of Radiation Sterilization on Properties of Biodegradable Lactide/Glycolide/Trimethylene Carbonate and Lactide/Glycolide/ε-caprolactone Porous Scaffolds with Shape Memory Behavior

by Piotr Rychter, Natalia Śmigiel-Gac, Elżbieta Pamuła, Anna Smola-Dmochowska, Henryk Janeczek, Wojciech Prochwicz and Piotr Dobrzyński

Materials 2016, 9(1), 64; https://doi.org/10.3390/ma9010064 - 20 Jan 2016

Cited by 16 | Viewed by 7792

Abstract

The aim of the study was the evaluation of gamma irradiation and electron beams for sterilization of porous scaffolds with shape memory behavior obtained from biodegradable terpolymers: poly(l-lactide-co-glycolide-co-trimethylene carbonate) and poly(l-lactide-co-glycolide-co-ɛ-caprolactone). The impact of mentioned sterilization techniques on the structure of the scaffolds before and after the sterilization process using irradiation doses ranged from 10 to 25 kGy has been investigated. Treatment of the samples with gamma irradiation at 15 kGy dose resulted in considerable drop in glass transition temperature (T_g) and number average molecular weight (M_n). For comparison, after irradiation of the samples using an electron beam with the same dose, no significant changes in structure or properties of examined scaffolds have been noticed. Higher doses of irradiation via electron beam caused essential changes of the scaffolds’ pores resulting in partial melting of their surface. Nevertheless, obtained results have revealed that sterilization with electron beam, when compared to gamma irradiation, is a better method because it does not affect significantly the physicochemical properties of the scaffolds. Both used methods of sterilization did not influence the shape memory behavior of the examined materials. Full article

(This article belongs to the Special Issue Biodegradable and Bio-Based Polymers)

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13 pages, 1303 KiB

Open AccessArticle

Poly-γ-Glutamic Acid: Biodegradable Polymer for Potential Protection of Beneficial Viruses

by Ibrahim R. Khalil, Victor U. Irorere, Iza Radecka, Alan T. H. Burns, Marek Kowalczuk, Jessica L. Mason and Martin P. Khechara

Materials 2016, 9(1), 28; https://doi.org/10.3390/ma9010028 - 6 Jan 2016

Cited by 28 | Viewed by 9261

Abstract

Poly-γ-glutamic acid (γ-PGA) is a naturally occurring polymer, which due to its biodegradable, non-toxic and non-immunogenic properties has been used successfully in the food, medical and wastewater industries. A major hurdle in bacteriophage application is the inability of phage to persist for extended periods in the environment due to their susceptibility to environmental factors such as temperature, sunlight, desiccation and irradiation. Thus, the aim of this study was to protect useful phage from the harmful effect of these environmental factors using the γ-PGA biodegradable polymer. In addition, the association between γ-PGA and phage was investigated. Formulated phage (with 1% γ-PGA) and non-formulated phage were exposed to 50 °C. A clear difference was noticed as viability of non-formulated phage was reduced to 21% at log₁₀ 1.3 PFU/mL, while phage formulated with γ-PGA was 84% at log₁₀ 5.2 PFU/mL after 24 h of exposure. In addition, formulated phage remained viable at log₁₀ 2.5 PFU/mL even after 24 h of exposure at pH 3 solution. In contrast, non-formulated phages were totally inactivated after the same time of exposure. In addition, non-formulated phages when exposed to UV irradiation died within 10 min. In contrast also phages formulated with 1% γ-PGA had a viability of log₁₀ 4.1 PFU/mL at the same exposure time. Microscopy showed a clear interaction between γ-PGA and phages. In conclusion, the results suggest that γ-PGA has an unique protective effect on phage particles. Full article

(This article belongs to the Special Issue Biodegradable and Bio-Based Polymers)

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15 pages, 649 KiB

Open AccessCommunication

Liquefied Wood as Inexpensive Precursor-Feedstock for Bio-Mediated Incorporation of (R)-3-Hydroxyvalerate into Polyhydroxyalkanoates

by Martin Koller, Miguel Miranda de Sousa Dias, Alejandra Rodríguez-Contreras, Matjaž Kunaver, Ema Žagar, Andrej Kržan and Gerhart Braunegg

Materials 2015, 8(9), 6543-6557; https://doi.org/10.3390/ma8095321 - 23 Sep 2015

Cited by 41 | Viewed by 6774

Abstract

Liquefied wood (LW) prepared in a microwave process was applied as a novel; inexpensive precursor feedstock for incorporation of (R)-3-hydroxyvalerate (3HV) into polyhydroxyalkanoate (PHA) biopolyesters in order to improve the biopolyester’s material quality; Cupriavidus necator was applied as microbial production strain. For proof of concept, pre-experiments were carried out on a shake flask scale using different mixtures of glucose and LW as carbon source. The results indicate that LW definitely acts as a 3HV precursor, but, at the same time, displays toxic effects on C. necator at concentrations exceeding 10 g/L. Based on these findings, PHA biosynthesis under controlled conditions was performed using a fed-batch feeding regime on a bioreactor scale. As major outcome, a poly(3HB-co-0.8%-3HV) copolyester was obtained displaying a desired high molar mass of M_w = 5.39 × 10⁵ g/mol at low molar-mass dispersity (Đ_M of 1.53), a degree of crystallinity (X_c) of 62.1%, and melting temperature T_m (176.3 °C) slightly lower than values reported for poly([R]-3-hydroxybutyrate) (PHB) homopolyester produced by C. necator; thus, the produced biopolyester is expected to be more suitable for polymer processing purposes. Full article

(This article belongs to the Special Issue Biodegradable and Bio-Based Polymers)

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19 pages, 2483 KiB

Open AccessReview

Antimicrobial Nanomaterials Derived from Natural Products—A Review

by Ji Wang and Wilfred Vermerris

Materials 2016, 9(4), 255; https://doi.org/10.3390/ma9040255 - 30 Mar 2016

Cited by 64 | Viewed by 9781

Abstract

Modern medicine has relied heavily on the availability of effective antibiotics to manage infections and enable invasive surgery. With the emergence of antibiotic-resistant bacteria, novel approaches are necessary to prevent the formation of biofilms on sensitive surfaces such as medical implants. Advances in nanotechnology have resulted in novel materials and the ability to create novel surface topographies. This review article provides an overview of advances in the fabrication of antimicrobial nanomaterials that are derived from biological polymers or that rely on the incorporation of natural compounds with antimicrobial activity in nanofibers made from synthetic materials. The availability of these novel materials will contribute to ensuring that the current level of medical care can be maintained as more bacteria are expected to develop resistance against existing antibiotics. Full article

(This article belongs to the Special Issue Biodegradable and Bio-Based Polymers)

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14 pages, 966 KiB

Open AccessReview

Newly Developed Techniques on Polycondensation, Ring-Opening Polymerization and Polymer Modification: Focus on Poly(Lactic Acid)

by Yunzi Hu, Walid A. Daoud, Kevin Ka Leung Cheuk and Carol Sze Ki Lin

Materials 2016, 9(3), 133; https://doi.org/10.3390/ma9030133 - 26 Feb 2016

Cited by 151 | Viewed by 25262

Abstract

Polycondensation and ring-opening polymerization are two important polymer synthesis methods. Poly(lactic acid), the most typical biodegradable polymer, has been researched extensively from 1900s. It is of significant importance to have an up-to-date review on the recent improvement in techniques for biodegradable polymers. This review takes poly(lactic acid) as the example to present newly developed polymer synthesis techniques on polycondensation and ring-opening polymerization reported in the recent decade (2005–2015) on the basis of industrial technique modifications and advanced laboratory research. Different polymerization methods, including various solvents, heating programs, reaction apparatus and catalyst systems, are summarized and compared with the current industrial production situation. Newly developed modification techniques for polymer properties improvement are also discussed based on the case of poly(lactic acid). Full article

(This article belongs to the Special Issue Biodegradable and Bio-Based Polymers)

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