Poly Acrylated Glycerol (PAG)
Homopolymer
Introduction
Materials and Experimental Procedure
Materials
Glycerol was purchased from fisher scientific. Amberlyst 15 was purchased from Octochem. Ethanox was
purchased from company X. Benzyl mercaptan, carbon disulfide, benzyl chloride, potassium phosphate
(tribasic), and Azobisisobutyronitrile were purchased from Sigma Aldrich. All chemicals were used
without any further purification.
Experimental
Synthesis of Dibenzyl Carbonotrithioate (DBCTT)
Synthesis of DBCTT was done using the methods detailed in Skey et. al (Jared Skey, 2008). 1 gram of
benzyl mercaptan was added to a stirred suspension of potassium phosphate (1.72 g) and acetone (20
mL). After ten minutes of stirring carbon disulfide (1.68 g) was added. An immediate yellow color change
was observed. After another ten minutes of stirring benzyl bromide was added (1.26 g) and an
immediate precipitation of potassium bromide was observed. Finally it was allowed to react for an
additional five minutes. The product was then filtered and washed with excess acetone. The solvent was
removed under vacuum and a product with 96% purity was recovered.
Synthesis of Acrylated Glycerol (AG)
Glycerol, acrylic acid, Ethanox, and Amberlyst -add amounts when optimization is complete- were mixed
together at 110°C for 5 hours. The conversion of acrylic acid was determined by NMR to be 30% (this
might change depending on optimization). The use of ethanox is to prevent the premature
polymerization of glycerol or acrylic acid, and the system was optimized to be the lowest amount
present to prevent this polymerization from occurring. The amount of amberlyst 15 was determined to
be the optimal amount based on conversion.
Acrylic acid is added at a 3.33 molar excess in order to achieve the desired functionality on glycerol-from
1:3 functional groups.
Synthesis of Poly Acrylated Glycerol (PAG)
AG is mixed with initiator (AIBN), solvent (unmodified glycerol), and chain transfer agent (DBCTT). The
amounts of solvent and DBCTT needed depend on desired molecular weight. After predetermined
reaction times, the polymer is then crashed out of solution using a 50/50 mixture of acetone and nhexanes. The polymer is then washed with acetone three times to remove any of the glycerol solvent.
Results
Acrylated Glycerol
Conversion
Conversion of Acrylic Acid
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
1
2
3
Time
Figure 1: Conversion of acrylic acid as a function of time
4
5
Figure 2:NMR of Acrylated Glycerol after 5 hours
Figure 3: NMR of Acrylated Glycerol after 5 hours zoomed into the acrylic region
Poly Acrylated Glycerol (PAG)
Table 1:Time to gellation as a function of cta to monomer ratio and concentration of monomer
Concentration of Monomer
[C]1
[C]2
[C]3
[C]4
[C]4
[C]4
[C]4
Ratio of CTA to Monomer
[CTA]1
[CTA]1
[CTA]1
[CTA]1
[CTA]2
[CTA]3
[CTA]4
Time to Gellation
t1
t2
t3
t4
t5
t6
T7
Table 2: GPC Reported Molecular Weight as a function of CTA:monomer ratio and number of acrylic groups
CTA to Monomer Ratio
[CTA]1
[CTA]2
[CTA]3
[CTA]4
[CTA]4
[CTA]4
[CTA]4
Number of Acrylic Groups
[C=C]1
[C=C]1
[C=C]1
[C=C]1
[C=C]2
[C=C]3
[C=C]4
Reported Molecular Weight
[Mw]1
[Mw]2
[Mw]3
[Mw]4
[Mw]5
[Mw]6
[Mw]7
Rheology as a Function of CTA:Monomer Ratio
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
0.5
1
1.5
2
2.5
3
3.5
4
Figure 4: Rheology of various CTA:monomer ratios at constant acrylation
4.5
5
Rheology as a Function of Degree of Acrylation
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
0.5
1
1.5
2
2.5
3
3.5
4
Figure 5:Rheology of various percent acrylation at constant cta:monomer ratio
Table 3: Glass Transition as a function of CTA:monomer ratio and number of acrylic groups
CTA:monomer ratio
[CTA]1
[CTA]2
[CTA]3
[CTA]4
[CTA]4
[CTA]4
[CTA]4
Acrylic Groups
[C=C]1
[C=C]1
[C=C]1
[C=C]1
[C=C]2
[C=C]3
[C=C]4
Glass Transition
T1
T2
T3
T4
T5
T6
T7
4.5
5