Characterization of the molecular weight distribution of polypropylene and polyethylene by turbidity at the lower critical solution temperature

1994 ◽  
Vol 72 (2) ◽  
pp. 390-397 ◽  
Author(s):  
Takouhi Bohossian ◽  
Geneviève Delmas ◽  
Henri Benoît
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Lower Critical Solution Temperature ◽  
Scattered Light ◽  
Solution Temperature ◽  
Atactic Polypropylene ◽  
Critical Solution Temperature ◽  
A New Technique

The characterization in butane of noncrystalline atactic polypropylene (ncPP) (1) with a narrow molecular weight distribution (MWD) is presented. It uses a new technique based on a thermogram, consisting of turbidity peaks developed in a solution at a Lower Critical Solution Temperature (LCST) during a step-by-step temperature increase. Several refinements concerning the analysis of data have been added to the expressions used in earlier work on polyethylene. The relation between the volume of the concentrated phase and the attenuation of light has been developed from an expression of the scattered light by a biphasic system. The thermograms gave a good agreement in Mw and Mw/Mn for four well-characterized ncPP samples. Wide MWD isotactic PP samples (2) were also analyzed in a mixture of butane and 2-methylbutane. Solution behavior at the LCST of 1 and 2 was compared.

A Progress in Development and Application of Size Exclusion Chromatograph/Multi-Angle Laser Light Scattering

2014 ◽  
Vol 936 ◽  
pp. 1597-1602
Author(s):  
Xue Yang ◽  
Ze Quan Liu ◽  
Qiang Zhang
Keyword(s):  
Molecular Weight ◽  
Light Scattering ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Laser Light ◽  
Laser Light Scattering ◽  
Size Exclusion

This paper reveals the development and significance of size exclusion chromatograph/multi-angle laser light scattering(SEC-MALLS) for determination of the molecular weight and characterization of the molecular weight distribution. This technque has been applied in many aspects, such as biology, polymer and carboxylate surfactant. It has made a big contribution to study the property of macromolecular substances.

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.

Synthesis and Characterization of Comb-Type Grafted Hydrogels

2012 ◽  
Vol 602-604 ◽  
pp. 1274-1284
Author(s):  
Ping Zhang ◽  
Shi Pu Li ◽  
Xin Yu Wang ◽  
Hong Lian Dai
Keyword(s):  
Aqueous Solution ◽  
Fluorescence Spectroscopy ◽  
Lower Critical Solution Temperature ◽  
Ammonium Persulfate ◽  
Solution Temperature ◽  
Synthesis And Characterization ◽  
Critical Solution Temperature

The grafted hydrogels of N-isopropylacrylamide (IPAAm) with 2-hydroxyethylacrylate (HEA) was prepared in an aqueous solution using ammonium persulfate (APS) and N,N,N’,N’-tetramethylethylene diamine (TEMED) as an accelerator. Lower critical solution temperature (LCST) and swelling ratios were measured as a function of temperature. The properties of the hydrogels contained pyrenyl probe in water were investigated by fluorescence spectroscopy.

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