What is the tacticity of PMMA?

The effects upon the glass transition temperature with differing tacticity is particularly noticeable in poly(methyl methacrylate), PMMA. Pure isotactic PMMA gives a Tg of around 42 0C whilst pure syndiotactic tends to be closer to 124 0C.

How do you find the degree of polymerization from NMR?

The Mn,NMR of the PEG-PGMA51 could be calculated using the following formulation: 5000+51*142=12242. Calculation of drug content from the 1H NMR results. ×100%=32.47% where n is the degree of polymerization of the relevant polymer, and MDOX, MGMA, MCBA, and MPEG is the molar mass of DOX, GMA, CBA and PEG, respectively.

What is tacticity and explain?

Tacticity (from Greek: τακτικός, romanized: taktikos, “relating to arrangement or order”) is the relative stereochemistry of adjacent chiral centers within a macromolecule. The practical significance of tacticity rests on the effects on the physical properties of the polymer.

Why are polymer NMR peaks broad?

For polymers however, resonance signals from repeating units often coalesce as broad peaks, even with high-field NMR spectrometers. This is largely due to poor molecular rotation and repeating units being situated in marginally different chemical environments.

Is PMMA isotactic?

PMMA exists in three different isomeric forms, namely, isotactic, syndiotactic, and atactic.

Does Tacticity affect glass transition temperature?

Summarizing this part, we have shown that the polymers’ tacticity influences the glass-transition dynamics. In the case of isotactic and syndiotactic PMMA, the relaxation processes are observed in different temperature ranges.

How do you determine the degree of polymerization?

Divide the molecular weight of the polymer by the molecular weight of the monomer unit to calculate the degree of polymerization. If the molecular mass of tetrafluoroethylene is 120,000, its degree of polymerization is 120,000 / 100 = 1,200.

What does the degree of polymerization indicate?

The degree of polymerization, or DP, is the number of monomeric units in a macromolecule or polymer or oligomer molecule. , where Mn is the number-average molecular weight and M0 is the molecular weight of the monomer unit.

What is isotactic and syndiotactic?

If all the methyl groups lie on the same side of the chain, the polymer is called isotactic. If the methyl groups alternate in a regular fashion from one side of the chain to the other, the polymer is syndiotactic.

What is isotactic configuration?

If all the substituents lie on one side of the chain the configuration is called isotactic. If the substituents alternate from one side to another in a regular manner the configuration is termed syndiotactic. Finally, a random arrangement of substituent groups is referred to as atactic.

Is syndiotactic PMMA crystalline?

1 Isotactic (it) PMMA and syndiotactic (st) PMMA can self-aggregate either by themselves or as stereocomplexes. it-PMMA crystals form a double-stranded helical structure,2 whereas st-PMMA does not crystallize, but includes specific organic solvents in a cavity within its single-stranded helix.

Is polymethyl methacrylate crystalline?

The it-PMMA 2D crystal is a 2D crystal and different from a conventional 3D crystal; however, its crystallographic parameters, the chain packing and the helical pitch of the chain, were in good agreement with the known values for the bulk crystal of it-PMMA.