**3.4 Molecular mechanics simulation of PNOBDME.**

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 nanostructures from helical polymers and metallic salts [41].

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

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 amide group enters along the lateral side chains.

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 in **Figure 16(c)**.

**Figure 15.** *Scheme of the spacer of PNOBDME including the two alcohol groups.*

#### **Figure 16.**

*Molecular simulation of PNOBDME monomer: (a) minimum energy MM model; (b) isotactic [PNOBDME]10; (c) cross-sectional view.*

#### **Figure 17.**

*The relationship between the four helical diastereomers gg and gt of the R and S enantiomers of PNOBDME and PNOBEE through the 11C▬12C\* bond, and 3 C▬<sup>4</sup> C\* (torsion φ), respectively.*

#### **3.5 Conformational analysis of PNOBDME and PNOBEE**

The tetrahedral carbon atoms **11C** in PNOBDME, allocated in *α* with respect to the asymmetric carbon atom 12C\* (**Figure 7(a)** with m = 9) and **3C** in PNOBEE, allocated in *α* with respect to chiral <sup>4</sup> C\* (**Figure 7(b)** with m = 1), along the polymer backbones, are referred as *prochirals*, since both could be converted into a chiral centre by arbitrarily changing only one attached H group to a deuterium atom (D with higher priority than H). Depending on the configuration, R/S, of the so created chiral centre, the H atom ideally deuterated, would be labeled as *pro-R*/*S*.

The two hydrogen atoms on the *prochiral 11C carbon atom*, Ha and Hb, in PNOBDME, can be described as *prochiral hydrogens*. Prochiral hydrogens can be also designated as *diastereotopic*. Their indistinguishable signals by <sup>1</sup> H-NMR split then into two signals easily differentiated. The same effect is observed for Hd and He, bonded to prochiral 10C, and for Hf and Hg, bonded to prochiral 9 C.

**93**

**Figure 19.**

*(c) Poly10\_PNOBDME\_Rgt; (d) Poly10\_PNOBDME\_Sgt*.

**Figure 18.**

*Cholesteric Liquid Crystal Polyesteramides: Non-Viral Vectors*

*Molecular model details of a PNOBDME dimer. View along 11C▬12C\* bond (perpendicular to the paper), with* 

*Molecular model details of PNOBDME polymers: (a) Poly10\_PNOBDME\_Rgg; (b) Poly10\_PNOBDME\_Sgg;* 

*(R) and (S) absolute configuration of 12C\* (in yellow behind 11C) for (a) Rgg-diasteroisomer;* 

*(b) Sgg-diasteroisomer; (c) Rgt-diasteroisomer; (d) Sgt diasteroisomer.*

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

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

#### **Figure 18.**

*Liquid Crystals and Display Technology*

*[PNOBDME]10; (c) cross-sectional view.*

**3.5 Conformational analysis of PNOBDME and PNOBEE**

*Molecular simulation of PNOBDME monomer: (a) minimum energy MM model; (b) isotactic* 

designated as *diastereotopic*. Their indistinguishable signals by <sup>1</sup>

bonded to prochiral 10C, and for Hf and Hg, bonded to prochiral 9

allocated in *α* with respect to chiral <sup>4</sup>

*and PNOBEE through the 11C▬12C\* bond, and 3*

The tetrahedral carbon atoms **11C** in PNOBDME, allocated in *α* with respect to the asymmetric carbon atom 12C\* (**Figure 7(a)** with m = 9) and **3C** in PNOBEE,

*C\* (torsion φ), respectively.*

polymer backbones, are referred as *prochirals*, since both could be converted into a chiral centre by arbitrarily changing only one attached H group to a deuterium atom (D with higher priority than H). Depending on the configuration, R/S, of the so created chiral centre, the H atom ideally deuterated, would be labeled as

*The relationship between the four helical diastereomers gg and gt of the R and S enantiomers of PNOBDME* 

*C▬<sup>4</sup>*

The two hydrogen atoms on the *prochiral 11C carbon atom*, Ha and Hb, in PNOBDME, can be described as *prochiral hydrogens*. Prochiral hydrogens can be also

into two signals easily differentiated. The same effect is observed for Hd and He,

C\* (**Figure 7(b)** with m = 1), along the

H-NMR split then

C.

**92**

*pro-R*/*S*.

**Figure 17.**

**Figure 16.**

*Molecular model details of a PNOBDME dimer. View along 11C▬12C\* bond (perpendicular to the paper), with (R) and (S) absolute configuration of 12C\* (in yellow behind 11C) for (a) Rgg-diasteroisomer; (b) Sgg-diasteroisomer; (c) Rgt-diasteroisomer; (d) Sgt diasteroisomer.*

**Figure 19.**

*Molecular model details of PNOBDME polymers: (a) Poly10\_PNOBDME\_Rgg; (b) Poly10\_PNOBDME\_Sgg; (c) Poly10\_PNOBDME\_Rgt; (d) Poly10\_PNOBDME\_Sgt*.

**Figure 20.**

*Molecular model details of PNOBDME polymers: (a) Poly60\_PNOBDME\_Rgg; Poly60\_PNOBDME\_Sgg; (c) Poly60\_PNOBDME\_Rgt; (d) Poly60\_PNOBDME\_Sgt*.

Equally the two hydrogen atoms on *prochiral 3 C carbon atom*, Ha and Hb, of PNOBEE, are considered as *prochiral hydrogens.*

Two independent sets of signals are experimentally observed by 1 H-NMR for each enantiomer of PNOBDME and PNOBEE [31]. They are related to the two possible staggered diastereomeric conformers, *gg* and *gt* of torsion *φ* along the 11C▬12C\* bond in PNOBDME and <sup>3</sup> C▬<sup>4</sup> C\* in PNOBEE, along the polymer backbone. One of these two systems is designated with an apostrophe (') and the other is designed without an apostrophe ().

The combination of a helix with two screw senses and the two absolute configurations by the presence of the asymmetric carbon atom provides four diastereomeric structures. There are two pairs of enantiomers each with two independent sets of <sup>1</sup> H-NMR signals. The four diastereomers of PNOBDME are depicted in **Figure 17**.

The existence of two independent conformers had also been observed for each enantiomer of PTOBDME and PTOBEE. It was also related to the presence of helical structures, the Cotton effect and the sign of the helicity in the case of 1-2 di-O-benzoylated sn-glycerols [33–39].

Details of molecular models for *gg* and *gt* conformers of a dimer of PNOBDME are shown (**Figure 18**), projected along the 11C▬12C\* bond and torsion *φ*

**95**

**Figure 19**.

**Figure 21.**

source.

(55.5 Å) and 0.029 Å<sup>−</sup><sup>1</sup>

**4. Conclusions**

*Cholesteric Liquid Crystal Polyesteramides: Non-Viral Vectors*

(perpendicular to the paper) with 12C\* (bonded to Hc) having *R* and *S* absolute

diastereomers, after minimizing the corresponding monomers are described in

Polymer models with 60 monomers of the 4 are exhibited in **Figure 20**.

**Figure 21(a)** and **(b)** shows the simultaneous SAXS/WAXS patterns of PNOBDME registered during heating from 30–200°C, with a synchrotron radiation

The SAXS spectra show two sharp order reflections at *q* value of 0.018 Å<sup>−</sup><sup>1</sup>

(d = 2.31 Å); and 40.75 (d = 2.01 Å) always remaining present in the entire tempera-

Peaks at 2θ ≅ 26.39 (d = 3.07 Å) and 50.71 (d = 1.73 Å) disappearing at about

The synthetic multifunctional cholesteric liquid crystal polyesteramides designed as PNOBDME (C34H38N2O6)n and PNOBEE (C26H22N2O6)n are reported as chemical modifications of multifunctional cholesteric LC polyesters, involving new

Molecular mechanics models of the new polymers show helical polymeric rigid chains. Homopolymerization was simulated with head-to-tail orientation and torsion angle between monomers fixed to 180°. Isotacticity was finally imposed on the polymer chains, explained in terms of the higher reactivity of the primary hydroxyl regarding the secondary one in the glycol through the polycondensation reaction.

enantiomer of PNOBDME and PNOBEE (while the R/S ratio of asymmetric carbon atoms remained 50:50) are related with two possible staggered diastereomeric conformers, *gg* and *gt* of torsion *φ*, containing the asymmetric carbon atom in the spacer, along the polymer backbone. One of these two systems is designated with an

properties but holding the precursor helical macromolecular structure.

Two independent sets of signals experimentally observed by <sup>1</sup>

(d = 4.38 Å); 18.83°

(d = 4.28 Å); 35.17

H-NMR for each

Helical polyesteramide (PNOBDME)10 molecular models obtained with the four

configuration, in yellow, behind 11C (bonded to Ha and Hb).

**3.6 Simultaneous SAXS/WAXS of PNOBDME**

*Simultaneous SAXS (a)/WAXS (b) patterns of PNOBDME.*

Four WAXS peaks, at 2θ ≅ 18.39°

(34.48 Å).

ture range, were assigned to the cholesteric mesophase.

90°C during the heating range are attributed to crystal 3D phase.

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

**Figure 21.**

*Liquid Crystals and Display Technology*

Equally the two hydrogen atoms on *prochiral 3*

C▬<sup>4</sup>

Two independent sets of signals are experimentally observed by 1

each enantiomer of PNOBDME and PNOBEE [31]. They are related to the two possible staggered diastereomeric conformers, *gg* and *gt* of torsion *φ* along the 11C▬12C\*

*Molecular model details of PNOBDME polymers: (a) Poly60\_PNOBDME\_Rgg; Poly60\_PNOBDME\_Sgg;* 

these two systems is designated with an apostrophe (') and the other is designed

The combination of a helix with two screw senses and the two absolute configurations by the presence of the asymmetric carbon atom provides four diastereomeric structures. There are two pairs of enantiomers each with two independent

H-NMR signals. The four diastereomers of PNOBDME are depicted in

The existence of two independent conformers had also been observed for each

Details of molecular models for *gg* and *gt* conformers of a dimer of PNOBDME

enantiomer of PTOBDME and PTOBEE. It was also related to the presence of helical structures, the Cotton effect and the sign of the helicity in the case of 1-2

are shown (**Figure 18**), projected along the 11C▬12C\* bond and torsion *φ*

PNOBEE, are considered as *prochiral hydrogens.*

*(c) Poly60\_PNOBDME\_Rgt; (d) Poly60\_PNOBDME\_Sgt*.

bond in PNOBDME and <sup>3</sup>

without an apostrophe ().

di-O-benzoylated sn-glycerols [33–39].

*C carbon atom*, Ha and Hb, of

C\* in PNOBEE, along the polymer backbone. One of

H-NMR for

**94**

sets of <sup>1</sup>

**Figure 20.**

**Figure 17**.

*Simultaneous SAXS (a)/WAXS (b) patterns of PNOBDME.*

(perpendicular to the paper) with 12C\* (bonded to Hc) having *R* and *S* absolute configuration, in yellow, behind 11C (bonded to Ha and Hb).

Helical polyesteramide (PNOBDME)10 molecular models obtained with the four diastereomers, after minimizing the corresponding monomers are described in **Figure 19**.

Polymer models with 60 monomers of the 4 are exhibited in **Figure 20**.

## **3.6 Simultaneous SAXS/WAXS of PNOBDME**

**Figure 21(a)** and **(b)** shows the simultaneous SAXS/WAXS patterns of PNOBDME registered during heating from 30–200°C, with a synchrotron radiation source.

The SAXS spectra show two sharp order reflections at *q* value of 0.018 Å<sup>−</sup><sup>1</sup> (55.5 Å) and 0.029 Å<sup>−</sup><sup>1</sup> (34.48 Å).

Four WAXS peaks, at 2θ ≅ 18.39° (d = 4.38 Å); 18.83° (d = 4.28 Å); 35.17 (d = 2.31 Å); and 40.75 (d = 2.01 Å) always remaining present in the entire temperature range, were assigned to the cholesteric mesophase.

Peaks at 2θ ≅ 26.39 (d = 3.07 Å) and 50.71 (d = 1.73 Å) disappearing at about 90°C during the heating range are attributed to crystal 3D phase.
