Triple shape memory polymers (TSMPs) are a growing subset of a class of smart materials known as shape memory polymers, which are capable of changing shape and stiffness in response to a stimulus. A TSMP can change shapes twice and can fix two metastable shapes in addition to its permanent shape. In this work, a novel TSMP system comprised of both permanent covalent cross-links and supramolecular hydrogen bonding cross-links has been synthesized via a one-pot method. Triple shape properties arise from the combination of the glass transition of (meth)acrylate copolymers and the dissociation of self-complementary hydrogen bonding moieties, enabling broad and independent control of both glass transition temperature (Tg) and cross-link density. Specifically, ureidopyrimidone methacrylate and a novel monomer, ureidopyrimidone acrylate, were copolymerized with various alkyl acrylates and bisphenol A ethoxylate diacrylate. Control of Tg from 0 to 60 °C is demonstrated: concentration of hydrogen bonding moieties is varied from 0 to 40 wt %; concentration of the diacrylate is varied from 0 to 30 wt %. Toughness ranges from 0.06 to 0.14 MPa and is found to peak near 20 wt % of the supramolecular cross-linker. A widely tunable class of amorphous triple-shape memory polymers has been developed and characterized through dynamic and quasi-static thermomechanical testing to gain insights into the dynamics of supramolecular networks.

An organocatalyzed ring-opening polymerization methodology was developed for the preparation of polycarbonates derived from glucose as a natural product starting material. The cyclic 4,6-carbonate monomer of glucose having the 1, 2, and 3 positions methyl-protected was prepared in three steps from a commercially available glucose derivative, and the structure was confirmed by means of NMR and IR spectroscopies, electrospray ionization mass spectrometry (MS), and single-crystal X-ray analysis. Polymerization of the monomer, initiated by 4-methylbenzyl alcohol in the presence of 1,5,7-triazabicyclo[4.4.0]dec-5-ene as the organocatalyst, proceeded effectively in a controlled fashion to afford the polycarbonate with a tunable degree of polymerization, narrow molecular weight distribution, and well-defined end groups, as confirmed by a combination of NMR spectroscopy, gel-permeation chromatography, and MALDI-TOF MS. A distribution of head-to-head, head-to-tail, and tail-to-tail regiochemistries was determined by NMR spectroscopy and tandem MS analysis by electron transfer dissociation. These polycarbonates are of interest as engineering materials because of their origination from renewable resources combined with their amorphous character and relatively high glass transition temperatures as determined by X-ray diffraction and differential scanning calorimetry studies.

Herein, we demonstrate the synthesis of a bicyclic carbonate monomer of a d-glucal derivative, which originated from the natural product d-glucose, in an efficient three-step procedure and its ring-opening polymerization (ROP), initiated by 4-methylbenzyl alcohol, via organocatalysis. The ROP behavior was studied as a function of time, catalyst type, and catalyst concentration by using size exclusion chromatography (SEC) and nuclear magnetic resonance (NMR) spectroscopy. Using a cocatalyst system of 1,8-diazabicyclo[5.4.0]­undec-7-ene and 1-(3,5-bis­(trifluoromethyl)­phenyl)-3-cyclohexyl-2-thiourea (5 mol %) afforded poly­(d-glucal-carbonate) (PGCC) with almost complete monomer conversion (ca. 99%) within 1 min, as analyzed by 1H NMR spectroscopy, and a monomodal SEC trace with dispersity of 1.13. The resulting PGCCs exhibited amorphous characteristics with a relatively high glass transition temperature at ca. 69 °C and onset decomposition temperature at ca. 190 °C, as analyzed by differential scanning calorimetry and thermogravimetric analysis, respectively. This new type of potentially degradable polymer system represents a reactive functional polymer architecture.

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A natural product-based polymer platform, having the characteristics of being derived from renewable materials and capable of breaking down, ultimately, into natural byproducts, has been prepared through the ring-opening polymerization (ROP) of a glucose-based bicyclic carbonate monomer. ROP was carried out via chain extension of a polyphosphoester (PPE) macroinitiator in the presence of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) organocatalyst to afford the PPE-b-poly(D-glucose carbonate) (PDGC) block copolymer. This new copolymer represents a functional architecture that can be rapidly transformed through thiol-yne reactions along the PPE segment into a diverse variety of amphiphilic polymers, which interestingly display stimuli-sensitive phase behavior in the form of a lower critical solution temperature (LCST). Below the LCST, they undergo self-assembly to form spherical core-shell nanostructures that display a poorly defined core-shell morphology. It is expected that hydrophobic patches are exposed within the micellar corona, reminiscent of the surface complexity of proteins, making these materials of interest for triggered and reversible assembly disassembly processes.

Strategies for the preparation of polycarbonates, derived from the natural product d-glucose, which have the potential to degrade back into their bioresorbable starting material and CO2, were developed. By employing established carbohydrate protection/deprotection chemistries, two d-glucose derivatives, methyl 4,6-O-benzylidene-α-d-glucopyranoside or methyl α-d-glucopyranoside, were converted into four different regioisomeric diol monomers, i.e., 1,4-, 1,6-, 2,6-, or 3,6-diols, as confirmed by nuclear magnetic resonance (NMR) spectroscopy, infrared (IR) spectroscopy, and mass spectrometry. Each type of regioisomeric monomer was then employed in a condensation polymerization with phosgene, generated in situ from triphosgene, as a comonomer, in the presence of pyridine, to produce four types of polycarbonates with different backbone regio-connectivity, as characterized by size exclusion chromatography, NMR spectroscopy, and IR spectroscopy. Interestingly, their thermal properties, i.e., glass transition temperature (T g) and thermal degradation behavior, were tunable by changing the topological composition of the monomeric unit. That is, polycarbonates with 2,6- and 3,6-backbone connectivity resulted in significantly higher T g of ca. 85 and 83 °C, respectively, as compared to those with 1,4- and 1,6-backbone connectivity, showing a T g of ca. 33 °C, as measured by differential scanning calorimetry. Furthermore, when the thermal decomposition temperature was measured by thermogravimetric analysis, the nonanomeric carbon backbone-based polycarbonates (2,6- and 3,6-) exhibited higher thermal stability and a sharper decomposition profile, with onset decomposition temperature (T d,onset) at 363 or 336 °C, as compared with those polymers containing the anomeric carbon in the carbonate linkage (1,4- and 1,6-), having T d,onset at 171 and 163 °C.

Polyurethane shape memory polymers (SMPs) with tunable thermomechanical properties and advanced processing capabilities have been synthesized, characterized, and implemented in the design of a microactuator medical device prototype. The ability to manipulate glass transition temperature (Tg) and crosslink density in low-molecular weight aliphatic thermoplastic polyurethane SMPs is demonstrated using a synthetic approach that employs UV catalyzed thiol-ene “click” reactions to achieve post-polymerization crosslinking. PUs containing varying C=C functionalization are synthesized, solution blended with polythiol crosslinking agents and photoinitiator and subjected to UV irradiation, and the effects of number of synthetic parameters on crosslink density are reported. Thermomechanical properties are highly tunable, including glass transitions tailorable between 30 and 105°C and rubbery moduli tailorable between 0.4 and 20 MPa. This new SMP system exhibits high toughness for many formulations, especially in the case of low crosslink density materials, for which toughness exceeds 90 MJ/m3 at select straining temperatures. To demonstrate the advanced processing capability and synthetic versatility of this new SMP system, a laser-actuated SMP microgripper device for minimally invasive delivery of endovascular devices is fabricated, shown to exhibit an average gripping force of 1.43 ± 0.37 N and successfully deployed in an in vitro experimental setup under simulated physiological conditions.

Nanocomposite polymers have been prepared using a new sustainable materials synthesis process in which d-Limonene functions simultaneously both as a solvent for recycling polystyrene (PS) waste and as a monomer that undergoes UV-catalyzed thiol-ene polymerization reactions with polythiol co-monomers to afford polymeric products comprised of precipitated PS phases dispersed throughout elastomeric poly(thioether) networks. These blended networks exhibit mechanical properties that greatly exceed those of either polystyrene or the poly(thioether) network homopolymers alone.