scholarly journals On the Optical Activity of Poly(l-lactic acid) (PLLA) Oligomers and Polymer: Detection of Multiple Cotton Effect on Thin PLLA Solid Film Loaded with Two Dyes

2020 ◽  
Vol 22 (1) ◽  
pp. 8
Author(s):  
Franco Cataldo
Keyword(s):  
Lactic Acid ◽  
Molecular Electronics ◽  
Optical Activity ◽  
High Efficiency ◽  
Field Effect Transistors ◽  
Optical Rotation ◽  
Optical Rotatory Dispersion ◽  
Poly Lactic Acid ◽  
Esterification Reaction ◽  
Model Composite

Optical rotatory dispersion (ORD) is a beautiful analytical technique for the study of chiral molecules and polymers. In this study, ORD was applied successfully to follow the degree of polycondensation of l-(+)-lactic acid toward the formation of poly(lactic acid) oligomers (PLAO) and high molecular weight poly(l-lactic acid) (PLLA) in a simple esterification reaction equipment. PLLA is a biodegradable polymer obtainable from renewable raw materials. The racemization of the intrinsically isotactic PLLA through thermal treatment can be easily followed through the use of ORD spectroscopy. Organic or molecular electronics is a hot topic dealing with the combination of π-conjugated organic compounds and polymers with specific properties (e.g., chirality) which can be exploited to construct optoelectronic devices, such as organic light-emitting diodes (OLEDs), organic photovoltaic (OPV) high efficiency cells, switchable chirality devices, organic field-effect transistors (OFETs), and so on. ORD spectroscopy was applied to study either the gigantic optical rotation of PLLA films, as well as to detect successfully the excitonic coupling, occurring in thin solid PLLA green film loaded with a combination of two dyes: SY96 (a pyrazolone dye) and PB16 (the metal-free phthalocyanine pigment). The latter compound PLLA loaded with SY96 and PB16 shows a really gigantic optical activity in addition to typical ORD signal due to exciton coupling and may be considered as a simple and easily accessible model composite of a chiral polymer matrix combined with π-conjugated dyes for molecular electronics studies.

Preparation of Poly(Lactic Acid) Acrylate for UV-Curable Coating Applications

2015 ◽  
Vol 659 ◽  
pp. 570-574 ◽  
Author(s):  
Apinya Musidang ◽  
Nantana Jiratumnukul
Keyword(s):  
Lactic Acid ◽  
Physical Properties ◽  
High Efficiency ◽  
Low Energy ◽  
Poly Lactic Acid ◽  
Coating Film ◽  
Pencil Hardness ◽  
Uv Curable ◽  
Low Energy Consumption ◽  
Volatile Organic

UV-curable process is widely used for paints, inks and adhesives due to its rapid curing, low energy consumption, high efficiency and low volatile organic compounds (VOCs). The objective of this research is to prepare poly(lactic acid) (PLA) based UV-curable coating by using glycolyzed PLA. PLA was glycolyzed by ethylene glycol (EG) at 170°C for 90 minutes. The obtained glycolyzed PLA was reacted with methacrylic anhydride (MAAH) to provide PLA acrylate oligomer. The obtained PLA acrylate oligomer was used in coating formulations with various amounts of photoinitiator and cured under UV radiation. Physical properties of cured coating film were investigated such as pencil hardness, gloss and haze. The results showed that poly(lactic acid) (PLA) based UV-curable coating provided good physical properties.

scholarly journals Star Shaped Long Chain Branched Poly (lactic acid) Prepared by Melt Transesterification with Trimethylolpropane Triacrylate and Nano-ZnO

Polymers ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 796 ◽  
Author(s):  
Le Yang ◽  
Zaijun Yang ◽  
Feng Zhang ◽  
Lijin Xie ◽  
Zhu Luo ◽  
...  
Keyword(s):  
Lactic Acid ◽  
High Efficiency ◽  
Synergistic Effects ◽  
Transesterification Reaction ◽  
Poly Lactic Acid ◽  
Cell Diameter ◽  
Nano Zno ◽  
Melt Strength ◽  
Trimethylolpropane Triacrylate ◽  
Long Chain

Long chain branched poly (lactic acid) (LCBPLA) was prepared via transesterification between high molecular weight poly (lactic acid) (PLA) and low molar mass monomer trimethylolpropane triacrylate (TMPTA) during melt blending in the presence of zinc oxide nanoparticles (nano-ZnO) as a transesterification accelerant in a torque rheometer. Compared with the traditional processing methods, this novel way is high-efficiency, environmentally friendly, and gel-free. The results revealed that chain restructuring reactions occurred and TMPTA was grafted onto the PLA backbone. The topological structures of LCBPLA were verified and investigated in detail. It was found that the concentration of the accelerants and the sampling occasion had very important roles in the occurrence of branching structures. When the nano-ZnO dosage was 0.4 phr and PLA was sampled at the time corresponding to the reaction peak in the torque curve, PLA exhibited a star-shaped topological structure with a high branching degree which could obviously affect the melt strength, extrusion foaming performances, and crystallization behaviors. Compared with pristine PLA, LCBPLA showed a higher melt strength, smaller cell diameter, and slower crystallization speed owing to the synergistic effects of nano-ZnO and the long chain branches introduced by the transesterification reaction in the system. However, severe degradation of the LCBPLAs would take place under a mixing time that was too long and lots of short linear chains generated due to the excessive transesterification reaction, with a sharp decline in melt strength.

scholarly journals Twins in YAl3(BO3)4 and K2Al2B2O7 Crystals as Revealed by Changes in Optical Activity

Crystals ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 8 ◽  
Author(s):  
Johannes Buchen ◽  
Volker Wesemann ◽  
Steffen Dehmelt ◽  
Andreas Gross ◽  
Daniel Rytz
Keyword(s):  
Optical Properties ◽  
Optical Activity ◽  
Nonlinear Optical ◽  
Frequency Conversion ◽  
Optical Rotation ◽  
Visible Spectrum ◽  
Rotatory Power ◽  
Nonlinear Optical Properties ◽  
Crystal Quality ◽  
Optical Rotatory Dispersion

Many borate crystals feature nonlinear optical properties that allow for efficient frequency conversion of common lasers down into the ultraviolet spectrum. Twinning may degrade crystal quality and affect nonlinear optical properties, in particular if crystals are composed of twin domains with opposing polarities. Here, we use measurements of optical activity to demonstrate the existence of inversion twins within single crystals of YAl 3 (BO 3 ) 4 (YAB) and K 2 Al 2 B 2 O 7 (KABO). We determine the optical rotatory dispersion of YAB and KABO throughout the visible spectrum using a spectrophotometer with rotatable polarizers. Space-resolved measurements of the optical rotation can be related to the twin structure and give estimates on the extent of twinning. The reported dispersion relations for the rotatory power of YAB and KABO may be used to assess crystal quality and to select twin-free specimens.

scholarly journals Controllable domain morphology in coated poly(lactic acid) films for high-efficiency and high-precision transportation of water droplet arrays

RSC Advances ◽  
2017 ◽  
Vol 7 (84) ◽  
pp. 53525-53531 ◽  
Author(s):  
Yongtao Wang ◽  
Huige Yang ◽  
Hongzhi Liu ◽  
Li Zhang ◽  
Ruixia Duan ◽  
...  
Keyword(s):  
Lactic Acid ◽  
High Precision ◽  
Water Droplet ◽  
High Efficiency ◽  
Adhesion Force ◽  
Superhydrophobic Surfaces ◽  
Poly Lactic Acid

Construction of superhydrophobic surfaces with tunable adhesion force has attracted considerable attention in past decades.

scholarly journals Influence of Lactic Acid Surface Modification of Cellulose Nanofibrils on the Properties of Cellulose Nanofibril Films and Cellulose Nanofibril–Poly (Lactic Acid) Composites

Biomolecules ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1346
Author(s):  
Ruth Anayimi Lafia-Araga ◽  
Ronald Sabo ◽  
Omid Nabinejad ◽  
Laurent Matuana ◽  
Nicole Stark
Keyword(s):  
Lactic Acid ◽  
Water Vapor ◽  
Water Absorption ◽  
Aqueous Medium ◽  
Cellulose Nanofibrils ◽  
Barrier Properties ◽  
Poly Lactic Acid ◽  
Esterification Reaction ◽  
Cellulose Nanofibril ◽  
Cnf Films

In this study, cellulose nanofibrils (CNFs) were modified by catalyzed lactic acid esterification in an aqueous medium with SnCl2 as a catalyst. Films were made from unmodified and lactic acid-modified CNF without a polymer matrix to evaluate the effectiveness of the modification. Ungrafted and lactic acid-grafted CNF was also compounded with poly(lactic acid) (PLA) to produce composites. Mechanical, water absorption, and barrier properties were evaluated for ungrafted CNF, lactic acid-grafted CNF films, and PLA/CNF composites to ascertain the effect of lactic acid modification on the properties of the films and nanocomposites. FTIR spectra of the modified CNF revealed the presence of carbonyl peaks at 1720 cm−1, suggesting that the esterification reaction was successful. Modification of CNF with LA improved the tensile modulus of the produced films but the tensile strength and elongation decreased. Additionally, films made from modified CNF had lower water absorption, as well as water vapor and oxygen permeability, relative to their counterparts with unmodified CNFs. The mechanical properties of PLA/CNF composites made from lactic acid-grafted CNFs did not significantly change with respect to the ungrafted CNF. However, the addition of lactic acid-grafted CNF to PLA improved the water vapor permeability relative to composites containing ungrafted CNF. Therefore, the esterification of CNFs in an aqueous medium may provide an environmentally benign way of modifying the surface chemistry of CNFs to improve the barrier properties of CNF films and PLA/CNF composites.

scholarly journals High-Toughness Poly(lactic Acid)/Starch Blends Prepared through Reactive Blending Plasticization and Compatibilization

Molecules ◽  
2020 ◽  
Vol 25 (24) ◽  
pp. 5951
Author(s):  
Huan Hu ◽  
Ang Xu ◽  
Dianfeng Zhang ◽  
Weiyi Zhou ◽  
Shaoxian Peng ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Performance Test ◽  
Mechanical Performance ◽  
Raw Materials ◽  
Amorphous Region ◽  
Poly Lactic Acid ◽  
Esterification Reaction ◽  
Melt Blending ◽  
Scanning Calorimetry ◽  
Starch Blends

In this study, poly(lactic acid) (PLA)/starch blends were prepared through reactive melt blending by using PLA and starch as raw materials and vegetable oil polyols, polyethylene glycol (PEG), and citric acid (CA) as additives. The effects of CA and PEG on the toughness of PLA/starch blends were analyzed using a mechanical performance test, scanning electron microscope analysis, differential scanning calorimetry, Fourier-transform infrared spectroscopy, X-ray diffraction, rheological analysis, and hydrophilicity test. Results showed that the elongation at break and impact strength of the PLA/premixed starch (PSt)/PEG/CA blend were 140.51% and 3.56 kJ·m−2, which were 13.4 and 1.8 times higher than those of pure PLA, respectively. The essence of the improvement in the toughness of the PLA/PSt/PEG/CA blend was the esterification reaction among CA, PEG, and starch. During the melt-blending process, the CA with abundant carboxyl groups reacted in the amorphous region of the starch. The shape and crystal form of the starch did not change, but the surface activity of the starch improved and consequently increased the adhesion between starch and PLA. As a plasticizer for PLA and starch, PEG effectively enhanced the mobility of the molecular chains. After PEG was dispersed, it participated in the esterification reaction of CA and starch at the interface and formed a branched/crosslinked copolymer that was embedded in the interface of PLA and starch. This copolymer further improved the compatibility of the PLA/starch blends. PEGs with small molecules and CA were used as compatibilizers to reduce the effect on PLA biodegradability. The esterification reaction on the starch surface improved the compatibilization and toughness of the PLA/starch blend materials and broadens their application prospects in the fields of medicine and high-fill packaging.

Effect of surface-modified silica on the thermal and mechanical behaviors of poly(lactic acid) and chemically crosslinked poly(lactic acid) composites

2019 ◽  
Vol 33 (12) ◽  
pp. 1692-1706 ◽  
Author(s):  
Chana Prapruddivongs ◽  
Jatsada Rukrabiab ◽  
Nuth Kulwongwit ◽  
Thapanee Wongpreedee
Keyword(s):  
Lactic Acid ◽  
Stearic Acid ◽  
Rice Husk ◽  
Crosslinking Agent ◽  
Poly Lactic Acid ◽  
Esterification Reaction ◽  
Different Types ◽  
The Fourier Transform ◽  
Surface Modified ◽  
Effect Of Surface

This work studied the properties of poly(lactic acid) (PLA) and chemically crosslinked poly(lactic acid) (CrPLA) in the presence of different types of silica (SiO2): SiO2 from rice husk ash (RhSiO2) and commercially available SiO2 (CoSiO2). A mixture of triallyl isocyanate and dicumyl peroxide was used as a chemical crosslinking agent. The rice husk was burnt in a furnace to extract RhSiO2. The thermal and mechanical properties of the PLA and CrPLA composites were investigated as a function of the SiO2 content. The presence of C–H functional groups supports the compatibility of stearic acid and RhSiO2, thereby facilitating the esterification reaction observed in the Fourier transform infrared-attenuated total reflectance spectra. This played an important role in changing the properties of the PLA-based composites. The concave fracture surfaces were consistent with the tensile results, the thermal properties, and the degree of swelling, which suggested that there was a better reaction between stearic acid and RhSiO2. However, the heat deflection temperatures of both the PLA and the CrPLA composites were not significantly affected by blending with either CoSiO2 or RhSiO2.

scholarly journals Improving the Toughness and Thermal Resistance of Polyoxymethylene/Poly(lactic acid) Blends: Evaluation of Structure–Properties Correlation for Reactive Processing

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 307 ◽  
Author(s):  
Jacek Andrzejewski ◽  
Katarzyna Skórczewska ◽  
Arkadiusz Kloziński
Keyword(s):  
Lactic Acid ◽  
Thermal Resistance ◽  
High Efficiency ◽  
Mechanical Performance ◽  
Softening Temperature ◽  
Thermomechanical Properties ◽  
Poly Lactic Acid ◽  
Reactive Processing ◽  
Scanning Calorimetry ◽  
The Impact

The study focuses on the development of polyoxymethylene (POM)/poly(lactic acid) (PLA) blends with increased impact and thermal resistance. The study was conducted in two phases; in the first part, a series of unmodified blends with PLA content of 25, 50, and 75 wt.% was prepared, while the second part focused on the modification of the PLA/POM (50/50) blends. An ethylene/butyl acrylate/glycidyl methacrylate terpolymer (E/BA/GMA) elastomer (EBA) was used to improve the impact strength of the prepared blends, while reactive blending was used to improve interfacial interactions. We used a multifunctional epoxy chain extender (CE) as the compatibilizer. Static tensile tests and notched Izod measurement were used to evaluate the mechanical performance of the prepared samples. The thermomechanical properties were investigated using dynamic mechanical thermal analysis (DMTA) analysis and heat deflection temperature (HDT)/Vicat softening temperature (VST) methods. The crystallinity was measured using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXS) measurements, while the rheology was evaluated using a rotational rheometer. The paper also includes a structure analysis performed using the SEM method. The structural tests show partial miscibility of the POM/PLA systems, resulting in the perfect compatibility of both phases. The impact properties of the final blends modified by the EBA/CE system were found to be similar to pure POM resin, while the E modulus was visibly improved. Favorable changes were also noticeable in the case of the thermomechanical properties. The results of most of the conducted measurements and microscopic observations confirm the high efficiency of the reaction for PLA as well as for the modified POM/PLA mixtures.

Synthesis and Characterization of Poly(Lactic Acid)-Grafted Natural Rubber by Reactive Melt-Blending Technique

2018 ◽  
Vol 382 ◽  
pp. 7-11
Author(s):  
Yodsathorn Wongngam ◽  
Cattaleeya Pattamaprom
Keyword(s):  
Lactic Acid ◽  
Natural Rubber ◽  
Ring Opening ◽  
Degree Of Polymerization ◽  
Hydroxyl Group ◽  
Synthesis And Characterization ◽  
Poly Lactic Acid ◽  
Esterification Reaction ◽  
Ring Opening Reaction

This study investigated the synthesis and characterization of poly(lactic acid)-grafted natural rubber (PLA-g-NR) in molten state. The grafting was carried out in an internal mixer without and with the presence of tin octoate catalyst (TO). The grafting of lactide onto NR was carried out by using maleic anhydride (MA) as a linker. The FTIR and 1H-NMR spectra revealed new peaks for the MA-grafted NR (NR-g-MA) and PLA indicating that MA was grafted onto NR and that LA was successfully polymerized into PLA. It was also found that MA grafted onto NR could assist as a linker for connecting PLA with NR via esterification reaction between hydroxyl group (OH) at the end chain of PLA and carboxylic group (COOH) from ring opening reaction of MA. Moreover, the decrease of residual LA peak in FTIR spectra suggested that the presence of TO catalyst in the reactive blend promoted higher degree of polymerization of PLA from ring opening reaction of LA.

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