scholarly journals Poly(glycolide) multi-arm star polymers: Improved solubility via limited arm length

2010 ◽  
Vol 6 ◽  
Author(s):  
Florian K Wolf ◽  
Anna M Fischer ◽  
Holger Frey
Keyword(s):  
Molecular Weight ◽  
Ring Opening ◽  
Biomedical Applications ◽  
Weight Control ◽  
Glycolic Acid ◽  
Polymer Melt ◽  
Degree Of Polymerization ◽  
Star Block Copolymers ◽  
Grafting From ◽  
Low Solubility

Due to the low solubility of poly(glycolic acid) (PGA), its use is generally limited to the synthesis of random copolyesters with other hydroxy acids, such as lactic acid, or to applications that permit direct processing from the polymer melt. Insolubility is generally observed for PGA when the degree of polymerization exceeds 20. Here we present a strategy that allows the preparation of PGA-based multi-arm structures which significantly exceed the molecular weight of processable oligomeric linear PGA (<1000 g/mol). This was achieved by the use of a multifunctional hyperbranched polyglycerol (PG) macroinitiator and the tin(II)-2-ethylhexanoate catalyzed ring-opening polymerization of glycolide in the melt. With this strategy it is possible to combine high molecular weight with good molecular weight control (up to 16,000 g/mol, PDI = 1.4–1.7), resulting in PGA multi-arm star block copolymers containing more than 90 wt % GA. The successful linkage of PGA arms and PG core via this core first/grafting from strategy was confirmed by detailed NMR and SEC characterization. Various PG/glycolide ratios were employed to vary the length of the PGA arms. Besides fluorinated solvents, the materials were soluble in DMF and DMSO up to an average arm length of 12 glycolic acid units. Reduction in the T g and the melting temperature compared to the homopolymer PGA should lead to simplified processing conditions. The findings contribute to broadening the range of biomedical applications of PGA.

scholarly journals Keggin-Type Heteropolyacid for Ring-Opening Polymerization of Cyclohexene Oxide: Molecular Weight Control

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Ahmed Aouissi ◽  
Zeid Abdullah Al-Othman ◽  
Abdurrahman Salhabi
Keyword(s):  
Molecular Weight ◽  
Reaction Time ◽  
Acetic Anhydride ◽  
Ring Opening ◽  
Weight Control ◽  
Reaction Medium ◽  
Resonance Spectroscopy ◽  
Cyclohexene Oxide ◽  
Scanning Calorimetry ◽  
Catalyst Amount

Polymerization of 1,2-cyclohexene oxide (CHO) in dichloromethane was catalyzed by 12-tungstophosphoric acid (H3PW12O40·13H2O) as a super solid acid. The effect of polymerization parameters such as reaction time, temperature, and catalyst amount was investigated. The effect of acetic anhydride as a ring-opening agent was also investigated. The resulting poly(1,2-cyclohexene oxide) (PCHO) was characterized by Fourier transform infrared (FTIR), nuclear magnetic resonance spectroscopy (1HNMR), gel-permeation chromatography (GPC), and differential scanning calorimetry (DSC). It has been found that the PCHO prepared over H3PW12O40·13H2O has a stereoregularity higher than that prepared over clay and Aluminium alkoxide catalysts. TheTgvalue obtained is due to the microstructure but not to molecular weight. The yield and the molecular weight of the polymer depend strongly on the reaction conditions. Molecular weights can be readily controlled by changing reaction temperature, reaction time, and catalyst amount. Contrary to most polymerization reactions, the molecular weight increases with the temperature increase. Addition of acetic anhydride to the reaction medium increased the yield threefold.

scholarly journals Tuning the Properties of High Molecular Weight Chitosans to Develop Full Water Solubility Within a Wide pH Range

2020 ◽  
Author(s):  
Anderson Fiamingo ◽  
Sergio Paulo Campana Filho ◽  
Osvaldo Novais Oliveira Junior
Keyword(s):  
Molecular Weight ◽  
Biomedical Applications ◽  
Random Distribution ◽  
Water Solubility ◽  
Aqueous Media ◽  
Degree Of Polymerization ◽  
Molecular Weights ◽  
H Nmr ◽  
Wide Ph Range ◽  
Ph Range

<p>The preparation of chitosans soluble in physiological conditions has been sought for years, but so far solubility in non-acidic aqueous media has only been achieved at the expense of lowering chitosan molecular weight. In this work, we applied the multistep ultrasound-assisted deacetylation process (USAD process) to β-chitin and obtained extensively deacetylated chitosans with high molecular weights (Mw ≥ 1,000,000 g mol<sup>-1</sup>). The homogeneous <i>N</i>-acetylation of a chitosan sample resulting from three consecutive USAD procedures allowed us to produce chitosans with a high weight average degree of polymerization (DPw ≈ 6,000) and tunable degrees of acetylation (DA from 5 to 80%). <i>N</i>-acetylation was carried out under mild conditions to minimize depolymerization, while preserving a predominantly random distribution of 2-amino-2-deoxy-D-glucopyanose (<i>GlcN</i>) and 2-acetamido-2-deoxy-D-glucopyanose (<i>GlcNAc</i>) units. This close to random distribution, inferred with deconvolution of nuclear magnetic resonance (<sup>1</sup>H NMR) spectra, is considered as responsible for the solubility within a wide pH range. Two of the highly <i>N</i>-acetylated chitosans (DA ≈ 60 % and ≈ 70 %) exhibited full water solubility even at neutral pH, which can expand the biomedical applications of chitosans. </p>

scholarly journals Molecular Weight Control via Cross Metathesis in Photo‐Redox Mediated Ring‐Opening Metathesis Polymerization

2020 ◽  
Vol 132 (23) ◽  
pp. 9159-9164
Author(s):  
Victoria K. Kensy ◽  
Rachel L. Tritt ◽  
Farihah M. Haque ◽  
Laura M. Murphy ◽  
Daniel B. Knorr ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Ring Opening ◽  
Weight Control ◽  
Ring Opening Metathesis Polymerization ◽  
Metathesis Polymerization ◽  
Molecular Weight Control ◽  
Cross Metathesis

scholarly journals How to Determine the Role of an Additive on the Length of Supramolecular Polymers?

2020 ◽  
Vol 02 (02) ◽  
pp. 129-142 ◽  
Author(s):  
Elisabeth Weyandt ◽  
Mathijs F. J. Mabesoone ◽  
Lafayette N. J. de Windt ◽  
E. W. Meijer ◽  
Anja R. A. Palmans ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Weight Control ◽  
Degree Of Polymerization ◽  
Supramolecular Polymers ◽  
Molecular Weights ◽  
Molecular Weight Control ◽  
A Chain ◽  
And Control ◽  
Supramolecular Polymerization

In polymer chemistry, modulation of sequence and control over chain length are routinely applied to alter and fine-tune the properties of covalent (co)polymers. For supramolecular polymers, the same principles underlying this control have not been fully elucidated up to this date. Particularly, rational control over molecular weight in dynamic supramolecular polymers is not trivial, especially when a cooperative mechanism is operative. We start this review by summarizing how molecular-weight control has been achieved in seminal examples in the field of supramolecular polymerizations. Following this, we propose to classify the avenues taken to control molecular weights in supramolecular polymerizations. We focus on dynamic cooperative supramolecular polymerization as this is the most challenging in terms of molecular weight control. We use a mass-balance equilibrium model to predict how the nature of the interaction of an additive B with the monomers and supramolecular polymers of component A affects the degree of aggregation and the degree of polymerization. We put forward a classification system that distinguishes between B acting as a chain capper, a sequestrator, a comonomer, or an intercalator. We also highlight the experimental methods applied to probe supramolecular polymerization processes, the type of information they provide in relation to molecular weight and degree of aggregation, and how this can be used to classify the role of B. The guidelines and classification delineated in this review to assess and control molecular weights in supramolecular polymers can serve to reevaluate exciting systems present in current literature and contribute to broaden the understanding of multicomponent systems.

Poly(α-hydroxyacids) in biomedical applications: synthesis and properties of lactic acid polymers

e-Polymers ◽  
2010 ◽  
Vol 10 (1) ◽  
Author(s):  
Rodica Lipsa ◽  
Nita Tudorachi ◽  
Cornelia Vasile
Keyword(s):  
Lactic Acid ◽  
Ring Opening ◽  
Biomedical Applications ◽  
Glycolic Acid ◽  
Recent Literature ◽  
Poly Lactic Acid ◽  
Biodegradation Rate ◽  
Degradation Behaviour ◽  
Food Applications ◽  
Us Fda

AbstractPoly( -hydroxy acids), especially poly(glycolic acid) (PGA), poly(lactic acid) (PLA) and their copolymers poly(lactic-co-glycolic acid) (PLGA) are novel class of commodity polymers, also used in biomedical applications. They can be synthesized with a controlled biodegradation rate and are biocompatible, bioresorbable and approved by US Food and Drug Administration (US FDA) for clinical use. Lactic acid polymers are developed in medicine (sutures, implants, orthopaedics, tissue engineering), pharmacy (controlled drug delivery systems) as well as in packaging, agriculture (mulch films, seed preservation), food applications, etc. The paper reviews recent literature data concerning lactic acid polymers synthesis (polycondensation, ring opening polymerization), physical (thermophysical, solubility, miscibility), mechanical properties, degradation behaviour, emphasizing on the poly(α -hydroxyacids) and lactic acid polymers applications in medicine and pharmacy.

scholarly journals Metabolic Engineered Biocatalyst: A Solution for PLA Based Problems

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Sundus Riaz ◽  
Nosheen Fatima ◽  
Ahmed Rasheed ◽  
Mehvish Riaz ◽  
Faiza Anwar ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Metabolic Engineering ◽  
Ring Opening ◽  
Biomedical Applications ◽  
Ring Opening Polymerization ◽  
Packaging Material ◽  
Medical Implants ◽  
Direct Production ◽  
Conventional Methods ◽  
Direct Condensation

Polylactic acid (PLA) is a biodegradable thermoplastic polyester. In 2010, PLA became the second highest consumed bioplastic in the world due to its wide application. Conventionally, PLA is produced by direct condensation of lactic acid monomer and ring opening polymerization of lactide, resulting in lower molecular weight and lesser strength of polymer. Furthermore, conventional methods of PLA production require a catalyst which makes it inappropriate for biomedical applications. Newer method utilizes metabolic engineering of microorganism for direct production of PLA through fermentation which produces good quality and high molecular weight and yield as compared to conventional methods. PLA is used as decomposing packaging material, sheet casting, medical implants in the form of screw, plate, and rod pin, etc. The main focus of the review is to highlight the synthesis of PLA by various polymerization methods that mainly include metabolic engineering fermentation as well as salient biomedical applications of PLA.

scholarly journals Molecular Weight Control via Cross Metathesis in Photo‐Redox Mediated Ring‐Opening Metathesis Polymerization

2020 ◽  
Vol 59 (23) ◽  
pp. 9074-9079 ◽  
Author(s):  
Victoria K. Kensy ◽  
Rachel L. Tritt ◽  
Farihah M. Haque ◽  
Laura M. Murphy ◽  
Daniel B. Knorr ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Ring Opening ◽  
Weight Control ◽  
Ring Opening Metathesis Polymerization ◽  
Metathesis Polymerization ◽  
Molecular Weight Control ◽  
Cross Metathesis
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