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REPORT OF VISIT TO UNIVERSITY OF NORTH CAROLINA, DEPT. OF CHEMISTRY, CHAPEL HILL, NC.

DATES OF VISIT: 29^th November through 2^nd December

SUBMITTED BY: Siddharth Patwardhan

SUBMITTED TO: Dr. S. J. CLARSON

SCHEDULE OF THE VISIT

Day 1 (Nov 29^th):

1. Started 1^st stage of the core-shell polymerization reaction.

2. Noted all the equipment & instruments used.

3. Read PhD thesis on “Composite Polymer Particles in SCCO₂: Synthesis and Characterization”.

Day 2 (Nov 30^th):

1. Meeting with Dr. DeSimone

2. Started the 2^nd stage of the core-shell polymerization reaction.

3. Discussed about surfactant and initiator design / choice.

Day 3 (Dec 1^st):

1. Completed the Polymerization.

2. Discussed about surfactant synthesis / design.

3. Visited North Carolina State University’s continuous polymerization in CO₂ in dept. of Chemical Engg.

Step-by-Step Procedure for Polymerization

I] Polymerization of the core (PS):

1. Weigh AIBN (0.04 g) & PS-b-PFOA (0.2 g).
2. Set the reactor volume to approximately to 12 ml.
3. Purge reactor with Argon.
4. Add 2 ml of styrene to the reactor, using syringe.
5. Adjust the CO₂ inlet pressure of the syringe pump around 5200 psi, and start adding CO₂ to the reactor.
6. Fill the reactor up to 1200 psi.
7. Start heating & let the temperature rise to 60 ⁰ C.
8. Then add more CO₂ to pressurize the reactor to 5000 psi.
9. Close all valves & keep the mixture for almost 24 hours at 5000 psi and 65 ⁰ C.
10. The pressure is displayed by ordinary display device & the temperature is controlled using Omega CN 4400 controller and the heating tape.

Figure 1: Experimental setup.

II] Polymerization of the shell (PMMA)

1.     Weigh 0.073 g AIBN and add it to 20 ml MMA.

2.     Keep the mixture in ice bath & stir for 15 min.

3.     Filter the mixture with syringe filter, to avoid clogging of small particles in the HPLC pump.

4.     Prime and purge the HPLC Pump with Tetra Hydro Furan.

5.     Prime and purge the HPLC Pump with feed solution.

6.     Decrease the pressure of the reactor to 4800 psi by increasing the volume.

7.     Add the feed from the HPLC pump. Make sure that the input pressure is higher than 5000 psi.

8.     Add CO₂ to the reactor till pressure becomes 5100 psi.

9.     Decrease the pressure of the reactor by increasing volume to 5000 psi.

10.  Close all valves.

11.  Clean the HPLC pump.

12.  Keep the mixture for approximately 18 hrs at 5000 psi and 65⁰ C.

III] Removing Polymer from reactor

1. Stop the heating the reactor.
2. Put the reactor into ice bath & cool it to 25⁰ C.
3. Vent CO₂ into methanol or propanol to avoid any loss of polymer.
4. Put the reactor in reduced pressure to remove excess of monomer.
5. Remove the dry white polymer powder from the reactor.
6. The methanol can be treated to recover the polymer.

Comments:

1. For any system other than considered here, the initiator has to be investigated, as the same initiator may not give the same efficiency in some other systems. While studying for a new initiator, its half-life period should be taken into consideration.

2. Same is the case with the surfactant. For any new system a new surfactant has to be used.

3. All the operating parameters have to be developed for a new reaction.

4. For any new system the solubility of monomer, polymer, initiator and the surfactant has to be studied over a range of temperature and pressure.