**3.2 Morphology of PNOBDME**

The morphology of powdered PNOBDME without any previous treatment has been studied by SEM. In **Figure 13**, six details of the powder sample (a to f) are shown of the homogeneous spherical clusters of about 5 μm in diameter homogeneously dispersed.

#### **3.3 Optical activity**

Although synthesized from starting racemic materials, PNOBDME showed unexpected chirality. The first fraction of the polymer did not show a net optical activity but values fluctuated from positive to negative, but the second fraction presented a low but constant value +1.02°, at 598 nm; +1.65°, at 579 nm; and +2.9°, at 435 nm and a very high optical activity value between +600° and +950°, at 365 nm, depending on temperature. The same behaviour had been also observed in PTOBDME and PTOBEE.

The variation of the optical rotatory dispersion values (α) by the effect of time of the second fraction of PNOBDME is expressed in **Figure 14** as molar optical rotation *[Φ] = [α] M/100*, at 365 nm, at two different temperatures, 35°C and 25°C, being *M* the molecular weight of the polymer repeating unit.

At 35°C, the ORD of PNOBDME increases with time to a value approximate of 600°, preserved between 90 and 180 min. After that, it increases again to reach a value of 950°, getting stabilized after 360 min. After 120 min at 25°C, the ORD reaches a value of 600° conserved up to 9 hours.

In both cases, once the ORD value was stabilized to 600° and 950°, if the wavelength of the lamp changed from 365 to 435 nm and quickly returned to 365 nm, the ORD value initially decreased to +8.6 but recovered its value. This phenomenon is being reversible. The variation of ORD with time has been described in helical polyguanidines synthesized either from chiral monomers or from achiral monomers with chiral catalysts [33–39]. At the end of this article, the optical activity of PNOBEE has not been studied.

**91**

**Figure 15.**

in **Figure 16(c)**.

**Figure 14.**

*Cholesteric Liquid Crystal Polyesteramides: Non-Viral Vectors*

**3.4 Molecular mechanics simulation of PNOBDME.**

*Optical rotatory dispersion of PNOBDME second fraction at 25C and 35°C.*

nanostructures from helical polymers and metallic salts [41].

11C, is shown in **Figure 15** for the R enantiomer of 12C\*.

amide group enters along the lateral side chains.

*Scheme of the spacer of PNOBDME including the two alcohol groups.*

The structural fragment including a chiral secondary alcohol and a primary alcohol group (a beta-chiral 1,2-diol) is particularly interesting since it is present in many relevant natural products, such as sugars, nucleosides, glycerides [40], chiral

In the case of PNOBDME, the fragment in the spacer including the secondary alcohol group, bonded to chiral 12C\*, and the primary alcohol, bonded to prochiral

Molecular mechanics always predict helical macromolecular structures along the main chain for PNOBDME and PNOBEE, as formulated in **Figure 7**. Instead, no helical polymer models were attained in the computational calculations when the

Molecular mechanics modeling was performed for the PNOBDME monomer with Materials Studio Windows v. 2019 [42]. COMPASS-II force field was loaded, including both atomic mass and charge. A model of the monomer is shown in **Figure 16(a)**, with optimized geometry to a minimum of energy, -95 Kcal/mol. Monomer polymerization was simulated by defining the 11C atom as the *head atom,* within the *repeating unit*, and the O atom bonded to 13**'**C, as the *tail atom*, being 12C\* the chiral centre. Homopolymerization was then simulated with head-to-tail orientation and torsion angle between monomers fixed to 180°. Isotacticity was finally imposed on the polymer chain. The helical polymer model so obtained along the main chain is shown in **Figure 16(b)**. The perpendicular cross-section appears

*DOI: http://dx.doi.org/10.5772/intechopen.91317*

**Figure 13.** *SEM images of powdered PNOBDME.*

*Cholesteric Liquid Crystal Polyesteramides: Non-Viral Vectors DOI: http://dx.doi.org/10.5772/intechopen.91317*

*Liquid Crystals and Display Technology*

**3.2 Morphology of PNOBDME**

neously dispersed.

**3.3 Optical activity**

The morphology of powdered PNOBDME without any previous treatment has been studied by SEM. In **Figure 13**, six details of the powder sample (a to f) are shown of the homogeneous spherical clusters of about 5 μm in diameter homoge-

Although synthesized from starting racemic materials, PNOBDME showed unexpected chirality. The first fraction of the polymer did not show a net optical activity but values fluctuated from positive to negative, but the second fraction presented a low but constant value +1.02°, at 598 nm; +1.65°, at 579 nm; and +2.9°, at 435 nm and a very high optical activity value between +600° and +950°, at 365 nm, depending on temperature. The same behaviour had been also observed in PTOBDME and PTOBEE. The variation of the optical rotatory dispersion values (α) by the effect of time of the second fraction of PNOBDME is expressed in **Figure 14** as molar optical rotation *[Φ] = [α] M/100*, at 365 nm, at two different temperatures, 35°C and 25°C,

At 35°C, the ORD of PNOBDME increases with time to a value approximate of 600°, preserved between 90 and 180 min. After that, it increases again to reach a value of 950°, getting stabilized after 360 min. After 120 min at 25°C, the ORD

In both cases, once the ORD value was stabilized to 600° and 950°, if the wavelength of the lamp changed from 365 to 435 nm and quickly returned to 365 nm, the ORD value initially decreased to +8.6 but recovered its value. This phenomenon is being reversible. The variation of ORD with time has been described in helical polyguanidines synthesized either from chiral monomers or from achiral monomers with chiral catalysts [33–39]. At the end of this article, the optical activity of

being *M* the molecular weight of the polymer repeating unit.

reaches a value of 600° conserved up to 9 hours.

PNOBEE has not been studied.

**90**

**Figure 13.**

*SEM images of powdered PNOBDME.*

**Figure 14.** *Optical rotatory dispersion of PNOBDME second fraction at 25C and 35°C.*
