A degradable low molecular weight monomer system with lower critical solution temperature behaviour in water

2019 ◽  
Vol 55 (6) ◽  
pp. 782-785 ◽  
Author(s):  
Bo Zheng ◽  
Zheng Luo ◽  
Yan Deng ◽  
Qiao Zhang ◽  
Lingyan Gao ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Crown Ether ◽  
Small Molecule ◽  
Lower Critical Solution Temperature ◽  
Solution Temperature ◽  
Low Molecular Weight ◽  
Temperature Behaviour ◽  
Critical Solution Temperature

A small molecule system showing LCST was prepared and the degradation of the crown ether motif effectively altered the thermo-responsiveness.

Effect of the molecular weight on the lower critical solution temperature of poly(N,N-diethylacrylamide) in aqueous solutions

2001 ◽  
Vol 79 (12) ◽  
pp. 1870-1874 ◽  
Author(s):  
D G Lessard ◽  
M Ousalem ◽  
X X Zhu
Keyword(s):  
Molecular Weight ◽  
Lower Critical Solution Temperature ◽  
Molar Mass ◽  
Average Molecular Weight ◽  
Solution Temperature ◽  
Low Molecular Weight ◽  
Fractional Precipitation ◽  
Critical Solution Temperature ◽  
Molecular Weight Dependence ◽  
Critical Molecular Weight

The molecular weight dependence of the lower critical solution temperature of poly(N,N-diethylacrylamide) was studied with 11 samples of the polymer with a number-average molecular weight (Mn) ranging from 9.6 × 103 to 1.3 × 106 g mol–1 and relatively narrow polydispersity indices from 1.19 and 2.60. These samples were obtained by fractional precipitation of the polymer. LCST values of polymers were measured by turbidimetry and microcalorimetry. An inverse dependence of LCST on the molar mass was found and the LCST of the samples remained more or less a constant above a critical molecular weight of ca. 2 × 105 g mol–1. The enthalpy and the entropy changes as well as the LCST of the polymer depend strongly on the molar mass of the polymer, especially in low molecular weight range.Key words: poly(N,N-diethylacrylamide), LCST, thermosensitive, phase diagram, effect of molecular weight.

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.

Polymer Fractionation at a Lower Critical Solution Temperature Phase Boundary

1967 ◽  
Vol 40 (5) ◽  
pp. 1544-1552
Author(s):  
C. H. Baker ◽  
C. S. Clemson ◽  
G. Allen
Keyword(s):  
Molecular Weight ◽  
Phase Boundary ◽  
Lower Critical Solution Temperature ◽  
Solution Temperature ◽  
Temperature Phase ◽  
Critical Solution Temperature ◽  
Upper Critical Solution Temperature ◽  
Two Samples ◽  
Polymer Fractionation ◽  
Molecular Weight Fractions

Abstract The influence of pressure on a lower critical solution temperature is much more pronounced than on an upper critical solution temperature. Accordingly it is possible to control phase separation at a LCST phase boundary under isothermal conditions by merely adjusting the pressure on the system. An apparatus has been constructed to investigate the isothermal fractionation of polyisobutene in which precipitation is controlled by pressure. Two samples of polyisobutene of Mv=1.76×106 and 9.0×104 have been fractionated in isopentane solution so as to yield up to six and nine fractions respectively. The integral molecular weight distribution curves thus obtained are compared with those obtained from conventional fractionations at an UCST. The sensitivity of the method is poor with regard to the separation of low molecular weight fractions and degradation occurs at the higher temperatures to an appreciable extent.

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.

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