THE FORMATION AND PROPERTIES OF THREE-DIMENSIONAL POLYMERS: I. STATISTICS OF NETWORK POLYMERS

1949 ◽  
Vol 27b (2) ◽  
pp. 116-127 ◽  
Author(s):  
J. Bardwell ◽  
C. A. Winkler
Keyword(s):  
Molecular Weight ◽  
Chain Transfer ◽  
Three Dimensional ◽  
Insoluble Fraction ◽  
Cross Linking ◽  
Molecular Heterogeneity ◽  
Swelling Properties ◽  
Network Polymers ◽  
Probable Distribution ◽  
Most Probable Distribution

Theoretical treatments of the elastic and swelling properties of three-dimensional polymers are reviewed and the predicted influence of network structure discussed. An expression is obtained for the statistically most probable distribution of molecular weight for polymers terminated by chain transfer with a modifier. Depletion of modifier does not lead to a large increase in molecular heterogeneity. The formation of an insoluble fraction and the development of cyclic structures when such polymers are subjected to cross-linking conditions are treated by an application of the theory of gelation.

The polymerization of styrene by sulphuric acid - III. The molecular weight distribution

1961 ◽  
Vol 263 (1312) ◽  
pp. 75-81 ◽  
Keyword(s):  
Molecular Weight ◽  
Sulphuric Acid ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
High Conversion ◽  
Chain Growth ◽  
Characteristic Parameters ◽  
Relative Probability ◽  
Probable Distribution ◽  
Most Probable Distribution

The theory of the molecular weight distribution in polystyrenes initiated by sulphuric acid, described in part I, has been tested by preparation and fractionation of suitable low-yield polymer samples. The expected ‘most probable’ distribution is found in these samples, but not in a high-conversion polymer. The characteristic parameters of the distributions the relative probability of chain growth—agree with values calculated from the kinetic con­stants measured in part II.

scholarly journals Characterization of Recombinant Poliovirus 2A Protease; A Potential Anti-Viral Drug Target

2018 ◽  
Author(s):  
Amna Younus ◽  
Muhammad Faraz Bhatti ◽  
Nasar Virk ◽  
Muhammad Arshad ◽  
Hussnain Janjua ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Antiviral Drug ◽  
Three Dimensional ◽  
Insoluble Fraction ◽  
Vital Role ◽  
Dimensional Structure ◽  
Cell Protein ◽  
Iptg Induction ◽  
2A Protease

Poliovirus 2A protease (PV2Apro) plays a vital role in viral replication and down-regulation of host cell protein synthesis. In order to understand more concerning PV2Apro, the protein was over-expressed in bacteria following amplification using sense and antisense primers and cloning in pET15b. Several expression hosts were tested and BL21 (DE3) pLysS cells gave the best expression of PV2Apro with minimal unwanted protein expression following IPTG induction. The 2Apro protein was purified to homogeneity using column chromatography, its solubility determined and its molecular weight and composition determined by MALDI-TOF mass spectrometry. The protease was found in the insoluble fraction and the purified protein had a slightly lower molecular weight than predicted. Moreover, three dimensional structure was modelled using template 1z8r with 58% identity and validated using ramachandran plot. Results revealed that most of the residues lie in favoured and allowed regions. These findings could help in a better understanding of PV2Apro structure and inhibition thus, highlighting potential targets for antiviral drug development.

THE FORMATION AND PROPERTIES OF THREE-DIMENSIONAL POLYMERS: III. THE EFFECT OF NETWORK STRUCTURE ON ELASTIC PROPERTIES

1949 ◽  
Vol 27b (2) ◽  
pp. 139-150 ◽  
Author(s):  
J. Bardwell ◽  
C. A. Winkler
Keyword(s):  
Molecular Weight ◽  
Statistical Mechanics ◽  
Elastic Properties ◽  
Network Structure ◽  
Three Dimensional ◽  
Butyl Rubber ◽  
Rubber Elasticity ◽  
Cross Linking

The tension exerted by stretched rubber at a given temperature and elongation is determined by the initial molecular weight and the concentration of cross-linkages. With the copolymer of butadiene and styrene (GR-S) the effect of molecular weight on elastic properties is identical with that found by Flory for butyl rubber and arises from the inactivity of terminal chains. When the molecular weight is fixed, the retractive force is approximately linear with the degree of cross-linking, in agreement with the statistical mechanics of rubber elasticity.

scholarly journals Full-Vectorial 3D Microwave Imaging of Sparse Scatterers through a Multi-Task Bayesian Compressive Sensing Approach

2019 ◽  
Vol 5 (1) ◽  
pp. 19 ◽  
Author(s):  
Marco Salucci ◽  
Lorenzo Poli ◽  
Giacomo Oliveri
Keyword(s):  
Compressive Sensing ◽  
Inverse Scattering ◽  
Computational Efficiency ◽  
State Of The Art ◽  
Three Dimensional ◽  
Microwave Imaging ◽  
Source Inversion ◽  
Contrast Source Inversion ◽  
Probable Distribution ◽  
Most Probable Distribution

In this paper, the full-vectorial three-dimensional (3D) microwave imaging (MI) of sparse scatterers is dealt with. Towards this end, the inverse scattering (IS) problem is formulated within the contrast source inversion (CSI) framework and it is aimed at retrieving the sparsest and most probable distribution of the contrast source within the imaged volume. A customized multi-task Bayesian compressive sensing (MT-BCS) method is used to yield regularized solutions of the 3D-IS problem with a remarkable computational efficiency. Selected numerical results on representative benchmarks are presented and discussed to assess the effectiveness and the reliability of the proposed MT-BCS strategy in comparison with other competitive state-of-the-art approaches, as well.

Cross-Linked αsγt-Chain Hybrids in Plasma Clots Studied by 1D- and 2D Electrophoresis and Western Blotting

1993 ◽  
Vol 70 (03) ◽  
pp. 438-442 ◽  
Author(s):  
B Grøn ◽  
C Filion-Myklebust ◽  
S Bjørnsen ◽  
P Haidaris ◽  
F Brosstad
Keyword(s):  
Molecular Weight ◽  
Monoclonal Antibodies ◽  
Human Plasma ◽  
Western Blotting ◽  
Isoelectric Point ◽  
Factor Xiii ◽  
Cross Linking ◽  
2D Electrophoresis ◽  
Complex Phenomenon ◽  
Fibrinopeptide A

SummaryFibrinogen and fibrin related chains in reduced human plasma as well as the bonds interlinking partially cross-linked fibrin from plasma clots have been studied by means of 1D- and 2D electrophoresis and Western blotting. Immunovisualization of reduced plasma or partially cross-linked fibrin with monoclonal antibodies specific for the α-chains or the γ-chains have shown that several bands represent material belonging to both chains. In order to decide whether these bands constitute αγ-chain hybrids or superimposed α- and γ-chain dimers, the cross-linked material was separated according to both isoelectric point (pI) and molecular weight (MW) using Pharmacia’s Multiphor II system. Western blotting of the second dimension gels revealed that partially cross-linked fibrin contains αsγt-chain hybrids and γ- polymers, in addition to the well-known γ-dimers and α-polymers. The main αsγt-chain hybrid has a pI between that of the α- and the γ-chains, a MW of about 200 kDa and contains Aα-chains with intact fibrinopeptide A (FPA). It was also observed that soluble fibrinogen/fibrin complexes as well as partially cross-linked fibrin contain degraded α-dimers with MWs close to the γ-dimers. These findings demonstrate that factor XIII-catalyzed cross-linking of fibrin is a more complex phenomenon than earlier recognized.

scholarly journals Mechanical Behavior of Hydroxyapatite-Chitosan Composite: Effect of Processing Parameters

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 213
Author(s):  
Hamid Ait Said ◽  
Hassan Noukrati ◽  
Hicham Ben Youcef ◽  
Ayoub Bayoussef ◽  
Hassane Oudadesse ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Compressive Strength ◽  
Mechanical Strength ◽  
Bone Repair ◽  
Mechanical Stability ◽  
Three Dimensional ◽  
Processing Parameters ◽  
Composite Effect ◽  
Solid Liquid ◽  
The Impact

Three-dimensional hydroxyapatite-chitosan (HA-CS) composites were formulated via solid-liquid technic and freeze-drying. The prepared composites had an apatitic nature, which was demonstrated by X-ray diffraction and Infrared spectroscopy analyses. The impact of the solid/liquid (S/L) ratio and the content and the molecular weight of the polymer on the composite mechanical strength was investigated. An increase in the S/L ratio from 0.5 to 1 resulted in an increase in the compressive strength for HA-CSL (CS low molecular weight: CSL) from 0.08 ± 0.02 to 1.95 ± 0.39 MPa and from 0.3 ± 0.06 to 2.40 ± 0.51 MPa for the HA-CSM (CS medium molecular weight: CSM). Moreover, the increase in the amount (1 to 5 wt%) and the molecular weight of the polymer increased the mechanical strength of the composite. The highest compressive strength value (up to 2.40 ± 0.51 MPa) was obtained for HA-CSM (5 wt% of CS) formulated at an S/L of 1. The dissolution tests of the HA-CS composites confirmed their cohesion and mechanical stability in an aqueous solution. Both polymer and apatite are assumed to work together, giving the synergism needed to make effective cylindrical composites, and could serve as a promising candidate for bone repair in the orthopedic field.

scholarly journals Nano-Assemblies from Amphiphilic PnBA-b-POEGA Copolymers as Drug Nanocarriers

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1164
Author(s):  
Angeliki Chroni ◽  
Thomas Mavromoustakos ◽  
Stergios Pispas
Keyword(s):  
Molecular Weight ◽  
Chain Transfer ◽  
Raft Polymerization ◽  
Polymeric Nanocarriers ◽  
Reversible Addition ◽  
2D Noesy ◽  
Drug Nanocarriers ◽  
Glycol Methyl Ether ◽  
Different Molecular Weight

The focus of this study is the development of highly stable losartan potassium (LSR) polymeric nanocarriers. Two novel amphiphilic poly(n-butyl acrylate)-block-poly(oligo(ethylene glycol) methyl ether acrylate) (PnBA-b-POEGA) copolymers with different molecular weight (Mw) of PnBA are synthesized via reversible addition fragmentation chain transfer (RAFT) polymerization, followed by the encapsulation of LSR into both PnBA-b-POEGA micelles. Based on dynamic light scattering (DLS), the PnBA30-b-POEGA70 and PnBA27-b-POEGA73 (where the subscripts denote wt.% composition of the components) copolymers formed micelles of 10 nm and 24 nm in water. The LSR-loaded PnBA-b-POEGA nanocarriers presented increased size and greater mass nanostructures compared to empty micelles, implying the successful loading of LSR into the inner hydrophobic domains. A thorough NMR (nuclear magnetic resonance) characterization of the LSR-loaded PnBA-b-POEGA nanocarriers was conducted. Strong intermolecular interactions between the biphenyl ring and the butyl chain of LSR with the methylene signals of PnBA were evidenced by 2D-NOESY experiments. The highest hydrophobicity of the PnBA27-b-POEGA73 micelles contributed to an efficient encapsulation of LSR into the micelles exhibiting a greater value of %EE compared to PnBA30-b-POEGA70 + 50% LSR nanocarriers. Ultrasound release profiles of LSR signified that a great amount of the encapsulated LSR is strongly attached to both PnBA30-b-POEGA70 and PnBA27-b-POEGA73 micelles.

scholarly journals Characterization of Polycaprolactone Nanohydroxyapatite Composites with Tunable Degradability Suitable for Indirect Printing

Polymers ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 295
Author(s):  
Stephanie E. Doyle ◽  
Lauren Henry ◽  
Ellen McGennisken ◽  
Carmine Onofrillo ◽  
Claudia Di Bella ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Large Scale ◽  
Three Dimensional ◽  
Cell Number ◽  
Compressive Modulus ◽  
Degradation Rates ◽  
Scaffold Materials ◽  
Natural Tissue ◽  
Complete Regeneration

Degradable bone implants are designed to foster the complete regeneration of natural tissue after large-scale loss trauma. Polycaprolactone (PCL) and hydroxyapatite (HA) composites are promising scaffold materials with superior mechanical and osteoinductive properties compared to the single materials. However, producing three-dimensional (3D) structures with high HA content as well as tuneable degradability remains a challenge. To address this issue and create homogeneously distributed PCL-nanoHA (nHA) scaffolds with tuneable degradation rates through both PCL molecular weight and nHA concentration, we conducted a detailed characterisation and comparison of a range of PCL-nHA composites across three molecular weight PCLs (14, 45, and 80 kDa) and with nHA content up to 30% w/w. In general, the addition of nHA results in an increase of viscosity for the PCL-nHA composites but has little effect on their compressive modulus. Importantly, we observe that the addition of nHA increases the rate of degradation compared to PCL alone. We show that the 45 and 80 kDa PCL-nHA groups can be fabricated via indirect 3D printing and have homogenously distributed nHA even after fabrication. Finally, the cytocompatibility of the composite materials is evaluated for the 45 and 80 kDa groups, with the results showing no significant change in cell number compared to the control. In conclusion, our analyses unveil several features that are crucial for processing the composite material into a tissue engineered implant.

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