scholarly journals From dendrimers to fractal polymers and beyond

2013 ◽  
Vol 49 (spe) ◽  
pp. 67-84 ◽  
Author(s):  
Charles N. Moorefield ◽  
Anthony Schultz ◽  
George R. Newkome
Keyword(s):  
Molecular Weight ◽  
Building Blocks ◽  
Exact Mass ◽  
Precise Control ◽  
Materials Research ◽  
Mathematical Algorithms ◽  
Self Similar ◽  
Macromolecular Architecture ◽  
Fractal Materials ◽  
Unique Species

The advent of dendritic chemistry has facilitated materials research by allowing precise control of functional component placement in macromolecular architecture. The iterative synthetic protocols used for dendrimer construction were developed based on the desire to craft highly branched, high molecular weight, molecules with exact mass and tailored functionality. Arborols, inspired by trees and precursors of the utilitarian macromolecules known as dendrimers today, were the first examples to employ predesigned, 1 → 3 C-branched, building blocks; physical characteristics of the arborols, including their globular shapes, excellent solubilities, and demonstrated aggregation, combined to reveal the inherent supramolecular potential (e.g., the unimolecular micelle) of these unique species. The architecture that is a characteristic of dendritic materials also exhibits fractal qualities based on self-similar, repetitive, branched frameworks. Thus, the fractal design and supramolecular aspects of these constructs are suggestive of a larger field of fractal materials that incorporates repeating geometries and are derived by complementary building block recognition and assembly. Use of terpyridine-M2+-terpyridine (where, M = Ru, Zn, Fe, etc) connectivity in concert with mathematical algorithms, such as forms the basis for the Seirpinski gasket, has allowed the beginning exploration of fractal materials construction. The propensity of the fractal molecules to self-assemble into higher order architectures adds another dimension to this new arena of materials and composite construction.

Processability predictions for mechanically recycled blends of linear polymers

2020 ◽  
Vol 40 (9) ◽  
pp. 771-781
Author(s):  
Janne van Gisbergen ◽  
Jaap den Doelder
Keyword(s):  
Molecular Weight ◽  
Circular Economy ◽  
Melt Flow Index ◽  
Building Blocks ◽  
Experimental Designs ◽  
New Method ◽  
Flow Index ◽  
Linear Polymers ◽  
Combined Method

AbstractRecycling of thermoplastic polymers is an important element of sustainable circular economy practices. The quality of mechanically recycled polymers is a concern. A method is presented to predict the structure and processability of recycled blends of polymers based on processability knowledge of their virgin precursor components. Blending rules at molecular weight distribution level are well established and form the foundation of the new method. Two essential fundamental building blocks are combined with this foundation. First, component and blend structure are related to viscosity via tube theories. Second, viscosity is related to melt flow index via a continuum mechanics approach. Emulator equations are built based on virtual experimental designs for fast forward and reverse calculations directly relating structure to viscosity and processability. The new combined method is compared with empirical blend rules, and shows important similarities and also clear quantitative differences. Finally, the new method is applied to practical recycling quality challenges.

Biodegradable Polymers Derived from Amino Acids for Biological Applications

2010 ◽  
Vol 76 ◽  
pp. 30-35 ◽  
Author(s):  
Naomi Cohen-Arazi ◽  
Ilanit Hagag ◽  
Michal Kolitz ◽  
Abraham J. Domb ◽  
Jeoshua Katzhendler
Keyword(s):  
Amino Acids ◽  
Molecular Weight ◽  
Ring Opening ◽  
Building Blocks ◽  
Ring Opening Polymerization ◽  
Microwave Assisted Synthesis ◽  
Hydroxy Acids ◽  
Natural Amino Acids ◽  
Direct Condensation ◽  
Positively Charged

Optically active α-hydroxy acids derived from amino acids have been synthesized and polymerized into new biodegradable polyesters. The variety of functional side chains enables the design of positively charged, negatively charged, hydrophobic and hydrophilic chiral building blocks or any combination of these constituents. Hydroxy acids of 15 natural amino acids were prepared with retention of configuration using a straightforward and reliable method of diazotization of α-amino acids. Polyesters were synthesized from these hydroxy acids by a number of methods: direct condensation in bulk, microwave assisted synthesis and ring opening polymerization. The molecular weight of the prepared polymers ranges between 2000 to 5000Da for the direct condensation and the microwave methods, whereas the ring opening polymerization results in high molecular weight polymers (20000 to 30000Da). The polymers were analyzed for their optical activity (Circular Dichroism Spectroscopy), thermal properties (DSC), solubility, molecular weight and polydispersity (GPC), and aqueous degradation. These polymers were tested for their compatibility to neuronal cells growth and differentiation.

Well-defined alternative polymer semiconductor using large size regioregular building blocks as monomers: electrical and electrochemical properties

2018 ◽  
Vol 6 (21) ◽  
pp. 5662-5670 ◽  
Author(s):  
Bogyu Lim ◽  
Dang Xuan Long ◽  
Song-Yi Han ◽  
Yoon-Chae Nah ◽  
Yong-Young Noh
Keyword(s):  
Molecular Weight ◽  
Conjugated Polymers ◽  
Electrochemical Properties ◽  
Building Blocks ◽  
Synthetic Strategy ◽  
Large Size ◽  
Large Molecular Weight ◽  
Polymer Semiconductor

We report an effective synthetic strategy to achieve well-defined regioregular alternative conjugated polymers using large molecular weight regioregular monomers.

scholarly journals Exploring the Internal Radiative Efficiency of Selective Area Nanowires

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
A. Cavalli ◽  
J. E. M. Haverkort ◽  
E. P. A. M. Bakkers
Keyword(s):  
Solar Cell ◽  
High Growth ◽  
Optical Emission ◽  
Building Blocks ◽  
Growth Conditions ◽  
Material System ◽  
Solar Cell Application ◽  
Precise Control ◽  
Radiative Efficiency ◽  
Selective Area

Nanowires are ideal building blocks for next-generation solar cell applications. Nanowires grown with the selective area (SA) approach, in particular, have demonstrated very high material quality, thanks to high growth temperature, defect-free crystalline structure, and absence of external catalysts, especially in the InP material system. A comprehensive study on the influence of growth conditions and device processing on optical emission is still necessary though. This article presents an investigation of the nanowire optical properties, performed in order to optimize the internal radiative efficiency. In an initial preamble, the motivation for this study is discussed, as well as the morphology and crystallinity of the nanowires. The effect on the nanowire photoluminescence of several intrinsic and extrinsic parameters and factors are then presented in three sections: first, the influence of basic growth conditions such as the temperature and the precursor ratio is studied. Subsequently, the effects of varying dopant molar flows are explored, keeping in mind the intended solar cell application. Third, the manner in which the processing and the passivation affect the nanowire optical emission is discussed. Precise control of the growth conditions allows maximizing the nanowire internal radiative efficiency and thus their performance in solar cells and other optoelectronic devices.

scholarly journals Effect of Hydrophobic Interactions on Lower Critical Solution Temperature for Poly(N-isopropylacrylamide-co-dopamine Methacrylamide) Copolymers

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 991 ◽  
Author(s):  
Alberto García-Peñas ◽  
Chandra Sekhar Biswas ◽  
Weijun Liang ◽  
Yu Wang ◽  
Pianpian Yang ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Lower Critical Solution Temperature ◽  
Hydrophobic Interactions ◽  
Structural Information ◽  
Drug Carriers ◽  
Solution Temperature ◽  
Polymerization Degree ◽  
Tissue Engineering Scaffolds ◽  
Critical Solution Temperature ◽  
Precise Control

For the preparation of thermoresponsive copolymers, for e.g., tissue engineering scaffolds or drug carriers, a precise control of the synthesis parameters to set the lower critical solution temperature (LCST) is required. However, the correlations between molecular parameters and LCST are partially unknown and, furthermore, LCST is defined as an exact temperature, which oversimplifies the real situation. Here, random N-isopropylacrylamide (NIPAM)/dopamine methacrylamide (DMA) copolymers were prepared under a systematical variation of molecular weight and comonomer amount and their LCST in water studied by calorimetry, turbidimetry, and rheology. Structural information was deduced from observed transitions clarifying the contributions of molecular weight, comonomer content, end-group effect or polymerization degree on LCST, which were then statistically modeled. This proved that the LCST can be predicted through molecular structure and conditions of the solutions. While the hydrophobic DMA lowers the LCST especially the onset, polymerization degree has an important but smaller influence over all the whole LCST range.

scholarly journals Characterization of a Complex Mixture of Immunomodulator Peptides Obtained from Autologous Urine

2020 ◽  
Vol 2020 ◽  
pp. 1-7
Author(s):  
Alberto Fragoso ◽  
Mérida Pedraza-Jiménez ◽  
Laura Espinoza-González ◽  
María Luisa Ceja-Mendoza ◽  
Hugo Sánchez-Mercado ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Raw Materials ◽  
Complex Mixture ◽  
Size Exclusion ◽  
Exact Mass ◽  
Molecular Weight Range ◽  
Peptide Profile ◽  
Exclusion Chromatography ◽  
Chromatographic Profile ◽  
Peptide Profiles

A complex mixture of peptides plays a key role in the regulation of the immune system; different sources as raw materials mainly from animals and vegetables have been reported to provide these extracts. The batch-to-batch product consistency depends on in-process controls established. However, when an immunomodulator is a customized product obtained from the same volunteer who will receive the product to personalize the treatment, the criteria to establish the consistency between volunteers are different. In this sense, it is expected to have the same molecular weight range although the profile of peptide abundance is different. Here, we characterized the peptide profile of three extracts of an immunomodulator obtained from the urine of different volunteers suffering from three different diseases (i.e., allergic rhinitis, rheumatoid arthritis, and chronic rhinopharyngitis), using size exclusion chromatography (SEC) and mass spectrometry (MS). The peptides contained in the immunomodulators were stable after six months, stored in a refrigerator. Our results showed a chromatographic profile with the same range of low molecular weight (less than 17 kDa) in all analyzed samples by SEC; these results were also confirmed by MS showing an exact mass spectrum from 3 to 13 kDa. The fact that the peptide profiles were conserved during a six-month period at refrigeration conditions (2 to 8°C) maintaining the quality and stability of the immunomodulator supports the notion that it might be an alternative in the treatment of chronic hypersensibility disorders.

scholarly journals Design and synthesis of a bis-macrocyclic host and guests as building blocks for small molecular knots

2020 ◽  
Vol 16 ◽  
pp. 2314-2321
Author(s):  
Elizabeth A Margolis ◽  
Rebecca J Keyes ◽  
Stephen D Lockey ◽  
Edward E Fenlon
Keyword(s):  
Molecular Weight ◽  
Electrostatic Interactions ◽  
Second Generation ◽  
Building Blocks ◽  
Design And Synthesis ◽  
Host Compound ◽  
Novel Method ◽  
Trefoil Knots

The thread–link–cut (TLC) approach has previously shown promise as a novel method to synthesize molecular knots. The modular second-generation approach to small trefoil knots described herein involves electrostatic interactions between an electron-rich bis-macrocyclic host compound and electron-deficient guests in the threading step. The bis-macrocyclic host was synthesized in eight steps and 6.6% overall yield. Ammonium and pyridinium guests were synthesized in 4–5 steps. The TLC knot-forming sequence was carried out and produced a product with the expected molecular weight, but, unfortunately, further characterization did not produce conclusive results regarding the topology of the product.

Sign in / Sign up

Export Citation Format

Share Document