Experimental method determination of osmotic pressure
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Experimental Method: Determination of  : Osmotic Pressure. The osmotic pressure data for cellulose tricaproate in dimethylformamide at three temperatures. The Flory  -temperature was determined to be 41 ± 1°C. Modified Flory-Huggins theory.  Is temperature dependent.

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Experimental method determination of osmotic pressure
Experimental Method:Determination of : Osmotic Pressure


The osmotic pressure data for cellulose tricaproate in dimethylformamide at three temperatures. The Flory -temperature was determined to be 41 ± 1°C


Modified flory huggins theory
Modified Flory-Huggins theory dimethylformamide at three temperatures. The Flory

 Is temperature dependent

Therefore, any temperature which causes =1/2 will

be the Flory  temperature


Flory huggins parameters
Flory-Huggins Parameters dimethylformamide at three temperatures. The Flory


An example
An Example dimethylformamide at three temperatures. The Flory


Applications of
Applications of dimethylformamide at three temperatures. The Flory 

The Chain Expansion Ratio and -Temperature

The Expansion Ratio, r


Applications of1
Applications of dimethylformamide at three temperatures. The Flory 

  • ardepends on balance between i) polymer-solvent and ii) polymer-polymer interactions

    • If (ii) are more favourable than (i)

      • ar< 1

      • Chains contract

      • Solvent is poor

    • If (ii) are less favourable than (i)

      • ar> 1

      • Chains expand

      • Solvent is good

    • If these interactions are equivalent, we have theta condition

      • ar = 1

      • Same as in amorphous melt


Applications of2
Applications of dimethylformamide at three temperatures. The Flory 

  • For most polymer solutions ardepends on temperature, and increases with increasing temperature

  • At temperatures above some theta temperature, the solvent is good, whereas below the solvent is poor, i.e.,

Often polymers will precipitate

out of solution, rather than contracting


Applications of3
Applications of dimethylformamide at three temperatures. The Flory 

The Solvent Goodness:

  • A Positive A2 indicates a good solvent, i.e. a solvent that gives rise to an exothermic enthalpy of mixing. This arise when <1/2.

  • When A2=0 the solvent is nearly Ideal. This is important for use of osmotic pressure to measure molar mass.

  • A negative A2 indicates a poor solvent (>1/2). The entalpy of mixing is positive here.

  • The goodness of solvent can be adjusted by changing the temperature.


Applications of4
Applications of dimethylformamide at three temperatures. The Flory 

Recall:

Note that the energy terms w11, w22 and w12 are attractive

terms and are usually negative .

When Hmix=0 for a solvent -polymer system, thus w11=w22 and

the cohesive energy density.


Summary
Summary dimethylformamide at three temperatures. The Flory

Solubility Parameters:

Thermodynamics of Mixing


Summary1
Summary dimethylformamide at three temperatures. The Flory

Free Energy of Mixing:


Summary2
Summary dimethylformamide at three temperatures. The Flory

Chemical Potential and Osmotic Pressure:


Summary3
Summary dimethylformamide at three temperatures. The Flory

Other Forms of Flory-Huggins Eqs:

0.35 (in older literature), or zero


Properties of
Properties of dimethylformamide at three temperatures. The Flory 

  • If the value of  is below 0.5, the polymer should be soluble if amorphous and linear.

  • When  equals 0.5, as in the case of the polystyrene–cyclohexane system at 34°C, then the Flory  conditions exist.

  • If the polymer is crystalline, as in the case of polyethylene, it must be heated to near its melting temperature, so that the total free energy of melting plus dissolving is negative.

  • For very many nonpolar polymer–solvent systems,  is in the range of 0.3 to 0.4.


Properties of1
Properties of dimethylformamide at three temperatures. The Flory 

  • For many systems,  has been found to increase with polymer concentration and decrease with temperature with a dependence that is approximately linear with, but in general not proportional to, 1/T.

  • For a given volume fraction 2 of polymer, the smaller the value of , the greater the rate at which the free energy of the solution decreases with the addition of solvent.

  • Negative values of  often indicate strong polar attractions between polymer and solvent.


Properties of2
Properties of dimethylformamide at three temperatures. The Flory 

  • The polymer–solvent interaction parameter is only slightly sensitive to the molecularweight.


Molecular weight averages
Molecular Weight Averages dimethylformamide at three temperatures. The Flory


Molecular weight distribution
Molecular Weight Distribution dimethylformamide at three temperatures. The Flory


Determination of number average mw
Determination of Number Average Mw dimethylformamide at three temperatures. The Flory

a) End-group Analysis

b) Colligative Properties


Osmotic pressure
Osmotic Pressure dimethylformamide at three temperatures. The Flory


Flory temperature
Flory dimethylformamide at three temperatures. The Flory -Temperature


Intrinsic viscosity
Intrinsic Viscosity dimethylformamide at three temperatures. The Flory


Some definitions
Some Definitions dimethylformamide at three temperatures. The Flory


The mark houwink relationship
The Mark-Houwink Relationship dimethylformamide at three temperatures. The Flory


Experimental techniques
Experimental Techniques dimethylformamide at three temperatures. The Flory


Example
Example dimethylformamide at three temperatures. The Flory


Example cont
Example (cont.) dimethylformamide at three temperatures. The Flory


Gel permiation chromatography
Gel dimethylformamide at three temperatures. The Flory Permiation Chromatography

Size Exclusion Chromatography


Schematic view
Schematic View dimethylformamide at three temperatures. The Flory


Calibration
Calibration dimethylformamide at three temperatures. The Flory

  • GPC is a relative Molecular Weight Method

  • Narrow molecular weight distribution, anionically polymerized polystyrenes are used most often.

  • Other Polymers: PMMA, Polyisoprene, polybutadiene, Poly(ethylene oxide) and sodium salts of PMA.


Calibration method
Calibration Method dimethylformamide at three temperatures. The Flory


Molecular weight of a suspension polymerized ps
Molecular Weight of a Suspension Polymerized PS dimethylformamide at three temperatures. The Flory


Gpc of a blend
GPC of a Blend dimethylformamide at three temperatures. The Flory


End of chapter 2
End of Chapter 2 dimethylformamide at three temperatures. The Flory


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