Comparative Properties of Ethyl, n -Butyl, and n -Octyl Cyanoacrylate Bioadhesives Intended for Wound Closure - Biologically Responsive Biomaterials for Tissue Engineering - page 101

a b

3

110

90

BCN Polymer

2

BCN Monomer BCN Monomer BCN Polymer

70

50

1

30

10

0

-10

0 100 200 300 400

0 100 200 300 400

Temperature (°C) Temperature (°C)

Fig. 5.11 ( a ) TGA thermograms of n -butyl cyanoacrylate monomer and polymer. ( b ) Derivative
curves of the TGA thermograms of n -butyl cyanoacrylate monomer and polymer

Table 5.6 Weight loss and temperature of the different decompositions of the cyanoacrylate
polymers
Polymer T1 (°C) Weight loss 1 (wt%) T2 (°C) Weight loss 2 (wt%)

ECN 196 99.1 - -

BCN 191 42.8 214 57.2

OCN 231 94.6 344 5.4

TGA experiments

the temperature at which decomposition is produced increases by increasing the length
of the alkyl hydrocarbon chain of the cyanoacrylate. Whereas the ECN polymer shows
a unique decomposition at 199 °C, both the n -butyl and the n -octyl cyanoacrylate poly-
mers show two thermal decompositions corresponding to two different structures.
SEM was used to analyze the topography of the cyanoacrylate polymers.
Figure 5.12 shows the SEM micrographs of the three polymers.
Whereas the ECN polymer shows a homogeneous and smooth surface, the
n -butyl and, more markedly, the n -octyl cyanoacrylate polymers show a heteroge-
neous topography consisting in shredded polymer chains. This indicates a different
extent of polymerization and the increase in the length of the alkyl hydrocarbon
chain cyanoacrylate produces less cohesive structure. This is in agreement with the
decrease in elastic modulus of the cyanoacrylate polymer by increasing the length
of the alkyl hydrocarbon chain reported elsewhere [ 16 ]. To the best of our knowl-
edge, this is the first time in the literature in which the differences in topography in
the polymerized cyanoacrylates are shown.

5.3.3 Adhesion Properties of Cyanoacrylate Adhesives

Adhesion properties of the cyanoacrylate monomers were measured by means of
single lap-shear tests. Aluminum/cyanoacrylate adhesive and pig skin/cyanoacry-
late adhesive joints were prepared to measure the adhesion of the bioadhesives once