Crystallization of short aliphatic chains. II. Example of even fold surface with adjacent fold reentry and of a transition to chain extension

1972 ◽  
Vol 10 (2) ◽  
pp. 239-252 ◽  
Author(s):  
L. D'ilario ◽  
A. Keller ◽  
E. Martuscelli
Keyword(s):  
Chain Extension ◽  
Aliphatic Chains

scholarly journals Poly(lactic Acid): A Versatile Biobased Polymer for the Future with Multifunctional Properties—From Monomer Synthesis, Polymerization Techniques and Molecular Weight Increase to PLA Applications

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1822
Author(s):  
Evangelia Balla ◽  
Vasileios Daniilidis ◽  
Georgia Karlioti ◽  
Theocharis Kalamas ◽  
Myrika Stefanidou ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Lactic Acid ◽  
Chain Extension ◽  
Poly Lactic Acid ◽  
Plastic Pollution ◽  
Practical Applications ◽  
Decomposition Reactions ◽  
Melt Polycondensation ◽  
Polymerization Conditions ◽  
Molecular Weight Increase

Environmental problems, such as global warming and plastic pollution have forced researchers to investigate alternatives for conventional plastics. Poly(lactic acid) (PLA), one of the well-known eco-friendly biodegradables and biobased polyesters, has been studied extensively and is considered to be a promising substitute to petroleum-based polymers. This review gives an inclusive overview of the current research of lactic acid and lactide dimer techniques along with the production of PLA from its monomers. Melt polycondensation as well as ring opening polymerization techniques are discussed, and the effect of various catalysts and polymerization conditions is thoroughly presented. Reaction mechanisms are also reviewed. However, due to the competitive decomposition reactions, in the most cases low or medium molecular weight (MW) of PLA, not exceeding 20,000–50,000 g/mol, are prepared. For this reason, additional procedures such as solid state polycondensation (SSP) and chain extension (CE) reaching MW ranging from 80,000 up to 250,000 g/mol are extensively investigated here. Lastly, numerous practical applications of PLA in various fields of industry, technical challenges and limitations of PLA use as well as its future perspectives are also reported in this review.

scholarly journals Characterization of Soil Organic Matter Individual Fractions (Fulvic Acids, Humic Acids, and Humins) by Spectroscopic and Electrochemical Techniques in Agricultural Soils

Agronomy ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1067
Author(s):  
Aleksandra Ukalska-Jaruga ◽  
Romualda Bejger ◽  
Guillaume Debaene ◽  
Bożena Smreczak
Keyword(s):  
Molecular Weight ◽  
Organic Matter ◽  
Soil Organic Matter ◽  
Humic Substances ◽  
Humic Acids ◽  
Agricultural Soils ◽  
Fulvic Acids ◽  
Sorption Properties ◽  
Aliphatic Chains

The objective of this paper was to investigate the molecular characterization of soil organic matter fractions (humic substances (HS): fulvic acids-FAs, humic acids-HAs, and humins-HNs), which are the most reactive soil components. A wide spectrum of spectroscopic (UV–VIS and VIS–nearIR), as well as electrochemical (zeta potential, particle size diameter, and polydispersity index), methods were applied to find the relevant differences in the behavior, formation, composition, and sorption properties of HS fractions derived from various soils. Soil material (n = 30) used for the study were sampled from the surface layer (0–30 cm) of agricultural soils. FAs and HAs were isolated by sequential extraction in alkaline and acidic solutions, according to the International Humic Substances Society method, while HNs was determined in the soil residue (after FAs and HAs extraction) by mineral fraction digestion using a 0.1M HCL/0.3M HF mixture and DMSO. Our study showed that significant differences in the molecular structures of FAs, Has, and HNs occurred. Optical analysis confirmed the lower molecular weight of FAs with high amount of lignin-like compounds and the higher weighted aliphatic–aromatic structure of HAs. The HNs were characterized by a very pronounced and strong condensed structure associated with the highest molecular weight. HAs and HNs molecules exhibited an abundance of acidic, phenolic, and amine functional groups at the aromatic ring and aliphatic chains, while FAs mainly showed the presence of methyl, methylene, ethenyl, and carboxyl reactive groups. HS was characterized by high polydispersity related with their structure. FAs were characterized by ellipsoidal shape as being associated to the long aliphatic chains, while HAs and HNs revealed a smaller particle diameter and a more spherical shape caused by the higher intermolecular forcing between the particles. The observed trends directly indicate that individual HS fractions differ in behavior, formation, composition, and sorption properties, which reflects their binding potential to other molecules depending on soil properties resulting from their type. The determined properties of individual HS fractions are presented as averaged characteristics over the examined soils with different physico-chemical properties.

Shear‐sensitive chain extension of dissolved poly(ethylene oxide) by aluminate ions

2020 ◽  
Author(s):  
Satyam Srivastava ◽  
Zachary Fink ◽  
Elizabeth G. Burns ◽  
Thomas P. Russell ◽  
David A. Hoagland
Keyword(s):  
Ethylene Oxide ◽  
Chain Extension ◽  
Poly Ethylene Oxide ◽  
Poly Ethylene

scholarly journals Enzymatic Synthesis of Muconic Acid-Based Polymers: Trans, Trans-Dimethyl Muconate and Trans, β-Dimethyl Hydromuconate

Polymers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2498
Author(s):  
Dina Maniar ◽  
Csaba Fodor ◽  
Indra Karno Adi ◽  
Albert J. J. Woortman ◽  
Jur van Dijken ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Renewable Resources ◽  
Enzymatic Synthesis ◽  
Enzyme Catalysis ◽  
Unsaturated Polyester ◽  
Chain Extension ◽  
Side Reactions ◽  
Muconic Acid ◽  
Thermal Stabilities ◽  
Polyester Resins

The vast majority of commodity polymers are acquired from petrochemical feedstock, and these resources will plausibly be depleted within the next 100 years. Therefore, the utilization of carbon-neutral renewable resources for the production of polymers is crucial in modern green chemistry. Herein, we report an eco-friendly strategy that uses enzyme catalysis to design biobased unsaturated (co)polyesters from muconic acid derivatives. This method is an attractive pathway for the production of well-defined unsaturated polyesters with minimum side reactions. A suite of characterization techniques was performed to probe the reaction mechanism and properties of the obtained polyesters. It is rationalized that the alkene functionality of the muconate monomers plays an important role in the enzyme catalysis mechanism. The rendered polyesters possessed excellent thermal stabilities and unreacted alkene functionality that can consecutively undergo chain extension, copolymerization, or act as an anchor for other functional groups. These properties open new avenues in the fields of unsaturated polyester resins and photosensitive coatings.

ChemInform Abstract: ONE CARBON-CHAIN EXTENSION FROM PRIMARY AMINES TO NITRILES VIA FORMAMIDES

1980 ◽  
Vol 11 (11) ◽  
Author(s):  
M. V. E. RODRIGUEZ ◽  
M. PORTENART ◽  
B. DELMON ◽  
H. G. VIEHE
Keyword(s):  
Carbon Chain ◽  
Chain Extension ◽  
Primary Amines

Synthesis and characterization of polyesteramides having short Nylon-6 segments in the main chains through polycondensation and chain extension

Polymer ◽  
2011 ◽  
Vol 52 (26) ◽  
pp. 6046-6055 ◽  
Author(s):  
Shiyue Liu ◽  
Chenguo Li ◽  
Jingbo Zhao ◽  
Zhiyuan Zhang ◽  
Wantai Yang
Keyword(s):  
Nylon 6 ◽  
Chain Extension ◽  
Synthesis And Characterization

Thermotropic mesomorphism of mixed-valent diruthenium aliphatic carboxylates with axial anion bearing two aliphatic chains

2013 ◽  
Vol 66 (19) ◽  
pp. 3380-3390 ◽  
Author(s):  
Tamara Bottazzi ◽  
Florencia Cecchi ◽  
Andrés Zelcer ◽  
Benoît Heinrich ◽  
Bertrand Donnio ◽  
...  
Keyword(s):  
Aliphatic Chains

scholarly journals Chain extension of ribonucleic acid by enzymes from rat liver cytoplasm

1968 ◽  
Vol 109 (4) ◽  
pp. 485-494 ◽  
Author(s):  
N. M. Wilkie ◽  
R. M. S. Smellie
Keyword(s):  
Rat Liver ◽  
Alkaline Hydrolysis ◽  
Actinomycin D ◽  
Chain Extension ◽  
Supernatant Fraction ◽  
Inorganic Pyrophosphate ◽  
Optimum Ph ◽  
Microsome Fraction ◽  
Hydrolysis Of ◽  
Generating System

1. The 105000g supernatant fraction of rat liver catalyses the incorporation of ribonucleotides from ribonucleoside triphosphates into polyribonucleotide material. The reaction requires Mg2+ ions and is enhanced by the addition of an ATP-generating system and RNA, ATP, UTP and CTP but not GTP are utilized in this reaction. In the case of UTP, the product is predominantly a homopolymer containing 2–3 uridine residues, and there is evidence that these may be added to the 3′-hydroxyl ends of RNA or oligoribonucleotide primers. 2. The microsome fraction of rat liver incorporates ribonucleotides from ATP, GTP, CTP and UTP into polyribonucleotide material. This reaction requires Mg2+ ions and is enhanced slightly by the addition of an ATP-generating system, and by RNA but not DNA. Supplementation of the reaction mixture with the three complementary ribonucleoside 5′-triphosphates greatly increases the utilization of a single labelled ribonucleoside 5′-triphosphate. The optimum pH is in the range 7·0–8·5, and the reaction is strongly inhibited by inorganic pyrophosphate and to a much smaller degree by inorganic orthophosphate. It is not inhibited by actinomycin D or by deoxyribonuclease. In experiments with [32P]UTP in the absence of ATP, GTP and CTP, 80–90% of 32P was recovered in UMP-2′ or −3′ after alkaline hydrolysis of the reaction product. When the reaction mixture was supplemented with ATP, GTP and CTP, however, about 40% of the 32P was recovered in nucleotides other than UMP-2′ or −3′. Although the reactions seem to lead predominantly to the synthesis of homopolymers, the possibility of some formation of some heteropolymer is not completely excluded.

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