Physics and Chemistry of Hybrid Organic-Inorganic Materials
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Physics and Chemistry of Hybrid Organic-Inorganic Materials Lecture 2: Characterizing the structure of Hybrids. Key points on how to characterize the structure of a hybrid material. appearance of the material solubility in organic solvents and water Amorphous versus crystalline materials

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Key points on how to characterize the structure of a hybrid material

Physics and Chemistry of Hybrid Organic-Inorganic MaterialsLecture 2: Characterizing the structure of Hybrids


Key points on how to characterize the structure of a hybrid material

Key points on how to characterize the structure of a hybrid material

  • appearance of the material

  • solubility in organic solvents and water

  • Amorphous versus crystalline materials

    • X-ray diffraction, calorimetry, dilatometry, SEM, TEM and AFM

  • Composition: Elemental analysis, x-ray techniques

  • Molecular level structure: X-ray (if crystalline), NMR, infrared or Raman spectroscopies.

  • Morphology: TEM, SEM, AFM, confocal fluorescence microscopy, optical microscopy

  • Fractal structures: small angle scattering (neutron or X-ray)

  • If soluble, molecular weight (Gel Permeation Chromatography, Vapor Phase Osmometry, Dynamic light scattering)


Hybrid materials

Hybrid Materials

Synthesis & Processing

Materials Science is a key field in studying hybrids

Properties

Structure

Function, Application,

Performance


First step in characterizing a hybrid

First step in characterizing a hybrid:

  • Use your senses (take pictures to document)

    • What color? Does it fluoresce

    • Transparent or opaque?

    • Homogeneous in appearance?

    • Solid or liquid

    • Tacky or sticky or brittle or tough

  • Mass – compare with theoretical yield


Describe the material below

Describe the material below


Describe the material below1

Describe the material below


Second try and dissolve the hybrid in different solvents

Second, try and dissolve the hybrid in different solvents

  • 50 milligrams of material in glass vial with 20 mL of: water, ethanol, benzene, methylene chloride, tetrahydrofuran, acetonitrile, hexane, acetone, diethyl ether, dimethyl sulfoxide, N-methyl pyrrolidone (NMP)

  • Leave samples in solvents at room temp overnight. Look for swelling if not dissolved.

  • Next, try boiling polymer in solvent for 4 hours.

  • If it doesn’t dissolve its probably cross-linked or really crystalline


Key points on how to characterize the structure of a hybrid material

Types of Polymers & solubility

soluble

insoluble

If swelling of polymer in solvent is observed: low low of crosslinking

No swelling, then highly crosslinked.


Structural characterization of soluble polymers

Structural Characterization of soluble polymers

  • 1H & 13C & 29Si Nuclear Magnetic Resonance and infrared spectroscopy

  • Molecular weight by gel permeation chromatography, dynamic light scattering, viscosity or vapor phase osomometry

  • Composition by combustion analyses

  • X-ray diffraction on film or powder

  • Viscosity of dilute solutions- shape of polymer


Nuclear magnetic resonance nmr spectroscopy

Nuclear Magnetic Resonance (NMR) Spectroscopy

  • Probably the most powerful and general technique for structural characterization

  • Uses radio frequency photon absorption to change nuclear spin states in 1H, 13C and 29Si atoms in molecules or materials

  • Most commonly used with samples in solution

  • Can also be used with insoluble solids

  • Signal chemical shift and coupling are used to determine structures.


Key points on how to characterize the structure of a hybrid material

Structure determination of organic compounds using NMR:

Types of protons & carbons present

Numbers of protons on each carbon

Number of protons on adjacent carbons

Stereochemistry of adjacent protons

Some longer distance information

Dissolve sample

in deuterated solvent

Place solution in

glass NMR tube

Run experiment

Work-up data


Solution nuclear magnetic resonance spectroscopy

Epoxide Open

Epoxide Closed

A)

B)

C)

Epoxide Open

Epoxide

Closed

Solution Nuclear Magnetic Resonance spectroscopy

  • Key tool in indentifying soluble polymers or figuring out their structure.

  • 1H, 13C and 29Si nuclei have spins of 1/2

13C NMR


Solid state nmr

Solid state NMR

Excellent tool for characterizing insoluble hybrids

Best with 13C and 29Si, not so good with 1H

β

γ

H3C

α

C=

C=O

H2C=

200 180 160 140 120 100 80 60 40 20 ppm

β

α

γ

200 180 160 140 120 100 80 60 40 20 ppm

Broader peaks than solution. More sample is required.


Infrared spectroscopy

Infrared Spectroscopy

  • Structural information based on bond vibrational absorptions in the infrared wavelengths.

  • Harder to determine structure than with NMR

  • Excellent for corroborating other characterization techniques.


Infrared spectrum of t8 phenyl silsesquioxane

Infrared spectrum of T8 Phenyl silsesquioxane


Key points on how to characterize the structure of a hybrid material

1790-1720

very strong

no

yes

1610 –1590,

1600 – 1580 and

1510 - 1490

1610-1590,

1600-1580 and

1510-1490

All numbers have the meaning of wave numbers

and are given in cm-1

3500 - 3200

840 - 820

3500 - 3200

1680 - 1630

strong

1450 -1410

sharp

strong

1450 - 1410

sharp

1550 - 1530

1100 - 1000

Polyvinyl

acetate,

PVC-copolymers

Modif.

Epoxies

Polycarbon-

ates

Phenol

derivatives,

Epoxies

Cellophan,

Alkylcellulose,

PVA, PEO

Polyamides,

amines

Alkylsilicone,

aliphatic hy

drocarbons,

Polytetra

fluorethylene

Thiokol

Acrylics,

Polyester

Cellulose

ester

Polyurethane

Alkyd-,

Polyesters,

Cellulose ether,

PVC(plasticized)

Polystyrenes,

Arylsilicones,

Aryl-alkyl Silicone Copolymers

PAN, PVC,

Polyvinylidene

chloride

POM

Nitrocellulose

cellophane

Identification of organic polymers using Infrared spectroscopy


Molecular weight determinations

Molecular Weight determinations

  • Only on soluble polymers

  • Different methods:

    • Gel permeation chromatography (MN, MW)

    • Dynamic Light scattering (MN, MW)

    • Viscosity (MV)

    • Vapor phase osmometry (MN)


Composition what elements are present and in what percent

Composition: What elements are present and in what percent

  • Organics are analyzed by combustion analysis

  • Inorganics may be analyzed by

    • emission or absorption spectroscopies

    • X-ray fluorescence

    • Elemental dispersive spectroscopy

  • The amount of inorganic in a hybrid can be determined gravimetrically by burning away all of the organic.


Amorphous versus crystalline

Amorphous versus crystalline

  • Amorphous – kinetic, no long range order, no time for crystals to grow from solution or liquid.

    How can you tell if a material is amorphous?

  • Crytsalline: thermdynamic structures made with reversiblity to remove defects and correct growth. Long range order.

    How can you tell if a material is crystalline?


Crystalline materials

Crystalline materials

  • Long range order: Bragg diffraction of electromagnetic radiation (or electron beams in TEM) by crystalline lattice into sharp peaks.

  • Solid structures with geometric shapes, straight lines and flat surfaces, and vertices.

  • Optical affects like bifringence

  • Direct visuallization of crystal at molecular level with AFM or STEM.

  • Melting point (not always though)


Key points on how to characterize the structure of a hybrid material

AFM of polyethylene crystallite

microcrystals

Inorganic crystals

XRD from semicrystalline

polymer film

Rutile titania crystals in amorphous TiO2

Micrograph of polymer crystalline spherulites


Xrd wide angle

XRD (wide angle)

  • Single crystal or microcrystalline powder (crystals with atomic or molecular scale order)


Xrd of crystalline material

XRD of crystalline material

2 theta plot

BCC iron


Amorphous materials

Amorphous materials

  • No long range order: diffuse peaks may be present, due to average heavy atom distances.

  • No crystalline geometries, glass like fractures (conchoidal)

  • Aggregate spherical particles common

  • Negative evidence for crystal at molecular level with AFM or STEM.

  • No Melting point


Key points on how to characterize the structure of a hybrid material

X-ray powder diffraction from polybenzylsilsesquioxane “LADDER” Polymer

4.2 A

3.1 A

Mostly amorphous material.

Small sharp peaks are due to contaminant from preparation

Not a ladder polymer!!!!!!!!!


Xrd amorphous material

XRD amorphous material

Al2O3 thin films prepared by spray pyrolysis

J. Phys.: Condens. Matter 13 No 50 (17 December 2001) L955-L959


Amorphous materials xrd

Amorphous materials: XRD

amorphous

amorphous

crystalline


Xrd of organic polymers

XRD of organic polymers

amorphous

semi-crystalline

crystalline


Conchoidal fractures in amorphous materials

Conchoidal Fractures in amorphous materials

Crystals break along miller planes

Unless microcrystalline


If crystals are small compared to impact conchoidal fracture can occur

If crystals are small compared to impact, conchoidal fracture can occur

In metal

In sandstone 3 meters tall)


Or third structural characterization of insoluble polymers

Or third, Structural Characterization of insoluble polymers

• Harder to characterize

• Does it burn (many inorganics do not)

  • Solid state 1H & 13C & 29Si Nuclear Magnetic Resonance and infrared spectroscopy

    • X-ray diffraction on film or powder

  • Composition by

    • combustion analyses if organic

    • X-ray fluorescence if inorganic


Electron microscopy

Electron Microscopy

  • Scanning electron microscopy (reflection)

  • Transmission electron microscopy (through sample)

TEM of surfactant templated silsesquioxane

TEM of amorphous hybrid

SEM of amorphous hybrid

SEM of surfactant templated

hybrid


Surface area measurements

Surface area measurements

  • Gas sorption porosimetry at the boiling point of the analysis gas (nitrogen).

  • Meassuring cell pressure after adsorption of gas in small doses on an evacuated sample of known mass generates a gas sorption isotherm.

  • Then you determine surface area, pore size, pore volume, pore size distribution from isotherm using mathematical models.


Morphological characterization of polymers

Morphological Characterization of polymers

  • If opaque or transluscent, SEM and optical microscopy (bifringence)-crystalline or amorphous & more.

  • Fracture polymer and look at fracture surfaces

  • Look for phase separation (like immiscible block copolymers)

  • Look for long range order

  • Look for pores


Morphology of hybrids

Morphology of hybrids

TEM, SEM and AFM are good tools for evaluating morphology

solid (1) phase of particles with pores. Other phase is gas.

One continuous phase (light); One planar dispersed phase (black)

Long range order, no particulate structure.

Two phases


Differential scanning calorimetry

Differential Scanning Calorimetry

Glass transition temperatures, melting points and reactions


Not every polymer needs all of these analyses but structure is the most basic and important

Not every polymer needs all of these analyses, but structure is the most basic and important

  • Known (described in literature) polymers need less structural characterization. Often just IR and Mw from GPC.

  • New polymers need complete structural characterization: NMR, IR, Combustion analysis, GPC, solubility, glass transition temp and/or melting point.


Summation

Summation

  • Characterization is key step in any science with hybrid materials

  • NMR, XRD, IR are central tools for characterization

  • Composition – including fraction inorganic to organic is also needed.

  • Determination if the material is ordered or not

  • Microscopic evaluation of morphology aids in identifying phase separated systems.


Key points on how to characterize the structure of a hybrid material

Literature procedure:

See how experimentals are written in good papers. Use them as model


Key points on how to characterize the structure of a hybrid material

Template for lab notebook:


Key points on how to characterize the structure of a hybrid material

Template for research labnotebook:


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