Chapter 1 - Microstructure, architecture and molar mass Flashcards
Name the different types of polymer architectures.
Please draw these polymer architectures as well.
Linear, cyclic, star, comb, branched, dendrimer.
What does “polymer” mean?
Poly - “many”
mer - “part”
What is a monomer?
A monomer is an atom or small molecule that may bind chemically to other monomers to form a polymer.
Define: “degree of polymerization”.
The degree of polymerization (n or N) is defined as the number of monomeric units in a polymer/oligomer-molecule.
Real polymer consists of chains with different lengths, and the degree of polymerization is therefore an average value.
What is an “oligomer”?
An oligomer is a molecule that consists of a few monomer units, in comparison with a “high” number of monomers for a polymer.
Name three main types of isomerism.
Please illustrate the different types.
Sequence isomerism, structural isomerism, stereo isomerism.
Which types of tacticity can a polymer have?
Draw a nice illustration to prove that you really know the difference between them.
Isotactic, syndiotactic, atactic.
Which types of molar mass definitions does one normally use for polymers?
Mathematically define them as well.
Number-average molar mass.
Weight average molar mass.
How is the polydispersity index defined?
Qualitatively describe what the PDI tell us.
The ratio between the weight average Mm and the number average Mm.
The polydispersity is a measure of the width of the distribution of our polymers.
Which two types of polymerization distributions are typically seen?
Draw the distribution and discuss when they appear.
Schulz-Zimmerman distribution: for step polymerization (polycondenzation).
Poisson-distribution: for chain polymerization.
For which molar masses is “osmometry” suited?
From 20000 to 1000000 g/mol.
Give one technique for determining the weight average molar mass.
Sketch the set-up.
Light scattering.
See book for setup.
What is the constitution of a polymer?
The constitution of a polymer describes the type and the order of the subunits (monomers) and the resulting molecular structure.
What is the “configuration” of a polymer?
The configuration of a polymer describes the spatial position of atoms within the molecule.
What is the “conformation” of a polymer?
Conformation is a description of the order that arises from the rotation of monomers around the single bonds. A description on how the 3D structure of the polymer is.
Name the different types of copolymers that exists, and what notation is used to describe them.
Random copolymer (P(A-ran-B)), diblock copolymer (PA-b-PB), triblock copolymer (PA-b-PB-b-PA), terblock copolymer (PA-b-PB-b-PC).
Explain how light scattering works. What information can we get from a light scattering experiment?
In a light scattering experiment, polarized (in x-direction) light is sent in the z-direction into a dilute solution. The oscillation of the electromagnetic field will cause oscillations of the molecules in the solution, scattering the light. A detector is placed at an angle theta in the yz-plane where it measures the intensity. The intensity of the light scattered from a unit volume of the solution is the sum of all the intensities from each molecule (N_tot/V = cN_a/M).
In a polydisperse solution, each species j with molar mass M_j contributes Kc_jM_j to the Rayleigh ratio. The sum over these yields KcM_w (since 1/c * ∑c_N * M_N = M_w). It therefore yields information on the weight-average molar mass.
What is the Rayleigh ratio?
The Rayleigh ratio is the ratio between the scattered intensity and the incident intensity, corrected for the distance between the scatter event and the detector.
R = I_scat * r^2 / I_i = KcM,
where K is an optical constant based on the
