Browsing by Author "David A. Shultz, Committee Member"

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Activation of Carbon-Hydrogen Bonds Mediated by Ru(II) Complexes
(2007-05-01) Pittard, Karl A.; David A. Shultz, Committee Member; James D. Martin, Committee Member; Edmond F. Bowden, Committee Member; T. Brent Gunnoe, Committee Chair
The RuII complex TpRu(CO)(NCMe)Me (Tp = hydridotris(pyrazolyl)borate) initiates carbon-hydrogen bond activation at the 2-position of furan and thiophene to produce methane and TpRu(CO)(NCMe)Ar (Ar = 2-furyl or 2-thienyl). Solid-state structures have been determined for TpRu(CO)(NCMe)(2-thienyl) and [TpRu(CO)(-C,S-thienyl)]2. The complex TpRu(CO)(NCMe)(2-furyl) serves as a catalyst for the formation of 2-ethylfuran from ethylene and furan. Similar catalytic reactivity was observed with TpRu(CO)(NCMe)(2-thienyl) for the production of 2-ethylthiophene. Density functional theory (DFT) calculations of the C-H activation of furan by {(TAB)Ru(CO)Me} (TAB = tris(azo)borate) indicate that the C-H activation sequence does not proceed through a RuIV oxidative addition intermediate. The reaction of TpRu(CO)(NCMe)Me and pyrrole forms TpRu(CO){ 2-N,N-(H)N=C(Me)(NC4H3)}. The formation of complex TpRu(CO){2-N,N-(H)N=C(Me)(NC4H3)} involves the cleavage of the N-H bond and 2-position C-H bond of pyrrole as well as a C-C bond forming step between pyrrole and the acetonitrile ligand of {TpRu(CO)(NCMe)}. Mechanistic studies indicate that the most likely reaction pathway involves initial metal-mediated N-H activation of pyrrole to produce TpRu(CO)(NCMe)(N-pyrrolyl) followed by C-C bond formation and proton transfer. Complex TpRu(CO)(NCMe)(N-pyrrolyl) has been independently prepared. At elevated temperatures, TpRu(CO)(NCMe)(N-pyrrolyl) converts to TpRu(CO){2-N,N-(H)N=C(Me)(NC4H3)}. Single crystal X-ray analysis has been achieved for TpRu(CO)(NCMe)(N-pyrrolyl), [TpRu(CO)(NCMe)(1-O-OC4H8) and TpRu(CO){2-N,N-(H)N=C(Me)(NC4H3)}. Computational studies support the suggested selectivity for initial N-H bond cleavage in preference to C-H bond activation. Rational design for a more electron-poor hydroarylation catalyst was discussed. Synthesis of Mp (Mp = tris(pyrazolyl)methane) complexes of the type [MpRu(PPh3)(CO)H]BAr'4, [MpRu(PPh3)(CO)Cl]BAr'4, [MpRu(PPh3)(PMe3)Cl]Cl, [MpRu(PPh3)(PMe3)Cl]BAr'4, [MpRu(PPh3)2Cl]BAr'4, [MpRu(PPh3){P(OMe)3}Cl]Cl, [MpRu(PPh3)(NCMe)Cl]BAr'4, [MpRu(PPh3)(NCMe)Cl]BAr'4 and [MpRu(PPh3)(CO)Cl]BAr'4 accomplished. A single-crystal X-ray diffraction study was carried out on the complex [MpRu(PPh3)(PMe3)Cl]Cl. [MpRu(PPh3)2Me]BAr'4 was prepared and examined by Cyclic Voltammetry (CV) where the E1/2 = 1.19 V. C-H activation was observed when [MpRu(PPh3)2Me]BAr'4 was heated in neat C6D6. Orthometalation appears to dominate reactivity via intramolecular C-H activation of a PPh3 ligand, however CH3D was produced at elevated temperatures. A series of Ep (Ep = tris(pyrazolyl)ethane) complexes of the type MpRu(Cl)2PR3 (R = Ph, OMe, or Me) were also synthesized. The [EpRu(PPh3)(NCMe)(Cl)]Cl and [EpRu(PPh3)(PMe3)(Cl)]Cl complexes were observed spectroscopically as intermediates in these syntheses. Improved synthesis of [MpRu(PPh3)2Cl]Cl was also accomplished by improving the yield by 23%, over the previously reported yield of 53%.
Asymmetric Polymerization initiated by Cationic Zirconocene Complexes possessing Chiral Counter Anions
(2006-08-07) Lee, Hyun-Su; Tonelli Alan E, Committee Member; Bruce M. Novak, Committee Chair; T. Brent Gunnoe, Committee Member; David A. Shultz, Committee Member
Chiral induction in cationic polymerization was studied. New cocatalysts, Sodium rac-tris(tetra-chlorobenzenediolato)phosphate(V) and triphenylcarbenium rac-tris(tetra-chlorobenzenediolato)phosphate(V) for cationic zirconocene complexes were synthesized, respectively. The X-ray single crystal structure of triphenylcarbenium tris(tetra-chlorobenzenediolato)phosphate(V) showed that the crystal structure is a racemic mixture and there are four ion pairs in the asymmetric unit and eight ion pairs in the unit cell. The most interesting part is that the distribution of delta-isomers and lambda-isomers is equal in the unit cell, but the anionic isomers in the asymmetric unit are predominantly (75%) one isomer. Poly (tert-butyl vinyl ether) samples were synthesized by the initiating system of bis(cyclopentadienyl)dimethylzirconium and triphenylcarbenium tris(tetra-chlorobenzenediolato)phosphate(V) and by the initiating system of Sodium tris(tetra-chlorobenzenediolato)phosphate(V) and bis(cyclopentadienyl)zirconiumdichloride. The polymers exhibited reasonable yields, reasonable molecular weights, and reasonable molecular weight distributions, respectively and both are atactic polymers. These two systems did not control the stereoregularity of the polymers. Chiral induction in coordination-insertion polymerization of carbodiimides was studied. New chiral cocatalysts, sodium delta-tris(tetra-chlorobenzenediolato)phosphate(V) and triphenylcarbenium delta-tris(tetra-chlorobenzenediolato)phosphate(V) for cationic zirconocene complexes possessing chiral counter anions were synthesized, respectively. The catalytic system with bis(cyclopentadienyl)dimethylzirconium and trityl rac-TRISPHAT polymerized carbodiimide monomers and the resulting polymers have reasonable yields. The asymmetric carbodiimide polymerization by using cationic zirconocene complexes with delta-TRISPHAT anion yielded polymers. Unfortunately, we did not observe chiral counter anion with cationic catalytic site can generate single handed helical polymer in this polymerization system. Using ¹H-NMR spectroscopy, a mononuclear cationic complex [Cp₂ZrCH₃][rac-TRISPHAT] formed in catalytic system with Cp₂Zr(CH₃)₂ and [CPh₃][rac-TRISPHAT] was studied. Addition of N,N'-di-n-hexylcarbodiimides to the catalytic system and further ¹H-NMR spectroscopic monitoring showed that the catalytic system [Cp₂ZrCH₃][rac-TRISPHAT] initiates and polymerizes N,N'-di-n-hexylcarbodiimides. A new chiral half-sandwich zirconium amidinate complex, CpZrCl₂[N(R)C(Me)N(R)] (R = (R)-1-cyclohexylethyl) was synthesized. A new synthetic method of new dianionic C₂H₂–bridged Cp⁄guanidinate ligands for new chiral catalysts was discovered.
Design and Synthesis of Porphyrins for Targeted Molecular Brachytherapy
(2007-12-21) Yao, Zhen; Dennis T. Brown, Committee Member; Winston Salser, Committee Member; Alexander Dieters, Committee Member; David A. Shultz, Committee Member; Jonathan S. Lindsey, Committee Chair
New approaches are urgently needed for treatment of cancer. The inherent heterogeneity of cells in solid tumors has thwarted most approaches developed to date. A fundamentally new approach, targeted molecular brachytherapy, also known as selective targeted amplified radiotherapy (S.T.A.R.), is attractive conceptually but has not yet been implemented. This new method selectively accumulates radioactive precipitates in tumor sites by systemic treatment of distinct agents in a sequential manner. One of the key agents for such a therapy is a soluble, precipitable reagent (SPR). The essence of this thesis includes design, synthesis and evaluation of porphyrin-based SPRs for the S.T.A.R. method. Three distinct designs of porphyrin-based SPRs were proposed. Synthetic approaches for target SPRs were explored, and several model compounds were synthesized. The development of a new synthetic approach to trans-AB-porphyrins, which are essential structures in the designs of SPRs, is also described in this thesis. Several target SPRs have not yet been synthesized due to synthetic difficulties as well as limitations related to water-solubility or stability of compounds. On the other hand, a diphosphate porphyrin exhibited successful enzymatic conversion from the water-soluble form to a porphyrin precipitate. Future work toward SPRs will focus on new designs that incorporate such diphosphate porphyrins.
Metal Catalyzed Polymerization of Cyclic Olefins
(2007-08-07) Seto, Keitaro; Dimitris S. Argyropoulos, Committee Member; Bruce M. Novak, Committee Chair; David A. Shultz, Committee Member; Jonathan S. Lindsey, Committee Member
We have been interested in polymerization of cyclic olefins using transition metal catalysts. Two important polymerization fashions have been studied, ring opening metathesis polymerization and coordination insertion polymerization. Various kinds of transition metal complex are known to catalyze the ring opening metathesis polymerization. Among those transition metal complex, ruthenium has a great advantage of less oxophilicity. A less oxophilic nature of ruthenium allows to polymerize functionalized monomer and to utilize alcohol⁄water as reaction medium. Several examples of the polymerization of functionalized monomer are known, however, very few of the polymerization in water is known. In addition, ring opening metathesis polymerization does not involve extra reagents and production of by products. From the green chemistry stand point, the utilization of water and clean reaction has a significant meaning. We have reported the investigation of the ring opening metathesis polymerization of oxo-functionalized cyclic olefin in water medium using ruthenium salt (Chapter 2). The polynorbornene from the coordination-insertion polymerization has great features as engineering plastics, and because of its properties many research projects of the coordination polymerization of norbornene have been done. Whereas, few examples of polymerization studies of other cyclic olefin have been reported. Among these cyclic olefins, particularly of cyclobutene derivatives have never been reported, which is because of the facile pericyclic ring opening reaction of cyclobutene during polymerization and ring opening metathesis polymerization as a side reaction. This our report is the first report that cyclobutene derivatives are polymerized without pericyclic ring opening reaction or ring opening metathesis polymerization to afford high molecular weight addition polymer (Chapter 3).
New Synthetic Routes to Porphyrins and Bacteriochlorins
(2008-08-01) Fan, Dazhong; Daniel L. Comins, Committee Member; Jonathan S. Lindsey, Committee Chair; David A. Shultz, Committee Member; Alexander Deiters, Committee Member
De Novo Synthesis of Stable Bacteriochlorins
(2005-03-29) Kim, Han-Je; Jonathan S. Lindsey, Committee Member; David A. Shultz, Committee Member; Daniel L. Comins, Committee Member; Christopher B. Gorman, Committee Member
Hydroporphyrins perform a wide variety of essential functions in living systems. Hydroporphyrins differ from porphyrins in having fewer pi bonds along the perimeter of the macrocycle. Efficient routes for the preparation of stable, dehydrogenation-resistant analogues of naturally occurring hydroporphyrins (e.g., chlorins, bacteriochlorins, isobacteriochlorins, corrins) are essential for fundamental studies and diverse applications. To develop such routes, a collection of 24 hydrodipyrrins has been prepared wherein each hydrodipyrrin contains a pyrrole ring and a pyrroline ring. The pyrroline ring bears a geminal-dimethyl group to lock-in the hydrogenation level. The alpha-substituents on the pyrrole and pyrroline rings provide different reactivity combinations (Nu/E⁺, E⁺/E⁺, or E⁺/Nu). Selected hydrodipyrrins have been employed in six exploratory routes to stable bacteriochlorins. The availability of straightforward routes to various hydrodipyrrins should facilitate development of syntheses of diverse hydroporphyrins (Chapter III). Bacteriochlorins are attractive for diverse photochemical applications owing to their strong absorption in the near-infrared spectral region, as exemplified by the bacterial photosynthetic pigment bacteriochlorophyll a, yet often are labile toward dehydrogenation to give the chlorin. An eight-step synthesis for preparing stable bacteriochlorins begins with p-tolualdehyde and proceeds to a dihydrodipyrrin-acetal (IV-1) bearing a geminal-dimethyl group and a p-tolyl substituent. Self-condensation of IV-1 in CH₃CN containing BF₃.OEt₂ at room temperature afforded a readily separable mixture of two free base bacteriochlorins and a ring-contracted, B,D-tetradehydrocorrin. Each bacteriochlorin contains two geminal-dimethyl groups to lock-in the bacteriochlorin (tetrahydroporphyrin) hydrogenation level, p-tolyl substituents at opposite (2,12) beta positions, and the absence (H-BC) or presence (MeO-BC) of a methoxy group at the 5- (meso) position. The B,D-tetradehydrocorrin (TDC) lies equidistant between the hydrogenation levels of corrin and corrole, is enantiomeric, and contains two geminal-dimethyl groups, 2,12-di-p-tolyl substituents, and an acetal group at the pyrroline-pyrrole junction. Examination of the effect of the concentrations of IV-1 (2.5 - 50 mM) and BF₃.OEt₂ (10 - 500 mM) revealed a different response surface for each of H-BC, MeO-BC, and TDC. The highest isolated yield of each was 49%, 30%, and 67%, respectively. The hydroporphyrins are stable to routine handling in light and air. The spectral features of H-BC are exemplary, including strong near-IR absorption (lambda[subscript Qy] = 737 nm, epsilon[subscript Qy] = 130,000 M⁻¹cm⁻¹) and emission (lambda[subscript em] = 744 nm, phi[subscript f] = 0.14). A crystal structure was obtained for MeO-BC. In summary, the ease of preparation of stable bacteriochlorins having characteristic spectral features should facilitate a wide variety of applications (Chapter IV).
Structure-Property Relationships for Electron Transfer Kinetics in Metal Tris(bipyridine) Core Dendrimers
(2005-07-28) Hong, Young-Rae; Edmond F. Bowden, Committee Member; Christopher B. Gorman, Committee Chair; David A. Shultz, Committee Member; Kenneth W. Hanck, Committee Member
Structure property relationship in the redox-active core dendrimers were systematically studied by probing the rate and driving force for electron transfer. An isostructural series of redox-active, metal tris(bipyridine) core dendrimers were synthesized for this purpose. Various synthetic routes were attempted to introduce the bulky dendritic moieties to the bipyridine units with high yields. Heterogeneous electron transfer kinetics was studied by electrochemical methods. In the second generation of these dendrimers, a large attenuation of electron transfer rate was observed qualitatively. A newly designed thin layer electrode was constructed and utilized to study heterogeneous electron transfer kinetics in the second generation dendrimers. In the finite condition, the slow heterogeneous electron transfer kinetics in second generation dendrimers could be studied by computer simulation. Homogeneous electron self-exchange kinetics was studied by nuclear magnetic resonance spectroscopy. The rate attenuation of electron transfer with dendrimer generation was not the same as the behavior found in heterogeneous, electrochemical electron transfer rate determinations. While a large attenuation was observed between the zeroth and first generation, the attenuation of electron transfer between the first and second generation was insignificant. This was rationalized by the concept of core mobility. The redox core in slow exchange limit can move in a non-rate limiting fashion toward a neighboring redox core with the result that the structural effect of the dendrimer is reduced and electron transfer is facilitated in larger dendrimers. For further studies, thermodynamic activation parameters were also obtained by variable temperature nuclear magnetic resonance studies.
Synthesis and Reactivity of Ruthenium and Platinum Complexes with Non-dative Heteroatomic Ligands: Studies of Carbon-hydrogen Bond Activation
(2007-12-18) Feng, Yuee; James D. Martin, Committee Member; David A. Shultz, Committee Member; Paul Maggard, Committee Member; T. Brent Gunnoe, Committee Chair
Several ruthenium complexes with non-dative heteroatomic ligands were prepared and fully characterized, including TpRu(PMe3)2X (X = OH, OPh, OMe, SH; Tp = hydridotris(pyrazolyl)borate). At elevated temperatures (90 °C — 130 °C), complexes of the type TpRu(PMe3)2X (X = OH, OPh, Me, Ph or NHPh) undergo regioselective H⁄D exchange with deuterated arenes. In addition, for X = OH or NHPh, H⁄D exchange occurs at hydroxo and anilido ligands, respectively. For X = OH, OPh, Me, Ph or NHPh, isotopic exchange occurs at the Tp 4-positions with only minimal deuterium incorporation at the Tp 3- or 5-positions. TpRu(PMe3)2Cl, TpRu(PMe3)2OTf (OTf = trifluoromethanesulfonate) and TpRu(PMe3)2SH do not initiate H⁄D exchange in C6D6 after extended periods of time at elevated temperatures. Mechanistic studies indicate that the likely pathway for the H⁄D exchange involves ligand dissociation (PMe3 or NCMe), Ru-mediated activation of an aromatic C-D bond, and deuteration of basic heteroatomic ligand (hydroxo or anilido) or Tp positions via intermolecular D+ transfer. The Ru(II) complexes TpRu(PMe3)2OR (R = H or Ph) react with excess phenylacetylene at elevated temperatures to produce the phenylacetylide complex TpRu(PMe3)2(CCPh). Kinetic studies indicate that the reaction of TpRu(PMe3)2OH and phenylacetylene likely proceeds through a pathway that involves TpRu(PMe3)2OTf as a catalyst. The reaction of TpRu(PMe3)2OH with 1,4-cyclohexadiene at elevated temperature forms benzene and TpRu(PMe3)2H, while TpRu(PMe3)2OPh does not react with 1,4-cyclohexadiene even after 20 days at 85 C. The paramagnetic Ru(III) complex [TpRu(PMe3)2OH][OTf] is formed upon single-electron oxidation of TpRu(PMe3)2OH with AgOTf. Reactivity studies suggest that [TpRu(PMe3)2OH][OTf] initiates reactions, including hydrogen atom abstraction, with C-H bonds that have bond dissociation energy ≤ 82 kcal⁄mol. Experimentally, the O-H bond strength of the Ru(II) cation [TpRu(PMe3)2(OH2)[OTf] is estimated to be between 82 and 85 kcal⁄mol, while computational studies yield a BDE of 84 kcal⁄mol, which are in reasonable agreement with the observed reactivity of [TpRu(PMe3)2OH]+. The preparation of the monomeric octahedral platinum(IV) complex (NCN')PtMe2NHPh (NCN' = 2,6-bis[(3,5-dimethylpyrazol-1-yl)methyl]bromobenzene) was achieved through metathesis of platinum triflate complex with alkali metal amido complex. This complex has been isolated and characterized by 1H NMR spectroscopy.
Synthesis of a Conjugated Ladder Polymer for Application in Direct Writing.
(2004-11-23) Monceaux, Christopher Jon; Christopher B. Gorman, Committee Chair; David A. Shultz, Committee Member; Jeffery L. White, Committee Member
Since the discovery of electroluminescence in conjugated polymers in 1990, electro-optic devices such as light emitting diodes, flat panel all polymer displays, and lasers have received a great deal of attention. Greater conjugation in these pi-electron systems leads to enhanced fluorescence and smaller band gaps. Upon this basis we have proposed exploiting these facets via a ladder polymer. A ladder polymer is an organic polymer that consists of linear molecules in which two cyclic subunits are linked together in a regular sequence, yielding a very rigid structure. Owing to their rigid structures and enhanced conjugation these materials would find many applications in nanoelectronics and high temperature environments, as well as exhibiting high laser damage thresholds. Several synthetic routes are proposed and explored attempting to successfully synthesize an A-B or A-A type monomer. This monomer will undergo palladium catalyzed alpha-arylation to form a processible precursor polymer which then will be chemically converted to an all aromatic ladder polymer.
Synthesis of Gold/Polymer Composites, Micelle/Polymer Composites, and Polymer Nanocapsules. Diffusion Studies and Encapsulation of Guest Molecules.
(2002-08-13) Marinakos, Efstathia (Stella) Maria; Daniel L. Feldheim, Committee Chair; Edmond F. Bowden, Committee Member; David A. Shultz, Committee Member; T. Brent Gunnoe, Committee Member
The template synthesis of core / shell particles is described. One template employed as the core is a gold particle. Polymers employed as the shell are polypyrrole, poly(N-methylpyrrole), and poly(3-methylthiophene). The gold core of the composite particle is removed to yield a hollow polymer capsule, the core dimensions of which are determined by the dimensions of the template. Shell thickness is also controlled easily. Permeability of the shell is varied according to shell composition, oxidation state of the polymer, and incorporated counterion. Attaching rhodamine B, anthraquinone, or horseradish peroxidase to the gold particle template prior to shell formation and removal of the core results in encapsulation of the molecule. A second template employed as the core is a micelle. Micelle core / polymer shell particles may possibly be further utlilized as an encapsulation method by solubilizing a molecule in the core of the micelle prior to polymer shell formation.
Synthetic Porphyrinic Macrocycles for Photodynamic Therapy and Other Biological Applications
(2008-04-06) Bhaumik, Jayeeta; Jonathan S. Lindsey, Committee Chair; David A. Shultz, Committee Member; T. Brent Gunnoe, Committee Member; Christian Melander, Committee Member
Synthetic porphyrinic macrocycles are invaluable for use in a wide variety of biological applications. Such applications include photodynamic therapy (PDT) for treatment of cancer, age-related macular degeneration (AMD), and microbial infections. Several metal chelates of protoporphyrin IX molecules [Zn(II), Pd(II), In(III), and Ga(III)] were prepared from the corresponding free base porphyrin. The metalloporphyrins were tested for anti-microbial PDT. Metalloporphyrins bearing cationic substituents showed better killing of gram-negative bacteria, whereas the free base porphyrin showed strong activity against gram-positive bacteria. Porphyrins bearing imidazolium substituents are valuable owing to the positive charge of the imidazolium group, which can impart water solubility to the porphyrin construct. To faciliate synthesis and handling of imidazole-substituted porphyrins, heteronuclear (11B, 15N) NMR spectroscopy was employed to fully characterize the various imidazole-substituted precursors to the porphyrins, including the dialkylboron complexes thereof. Metal chelates of imidazolium-porphyrins [Zn(II), Pd(II), and In(III)] were prepared starting from non-polar trans-AB porphyrins. Imidazolium-porphyrins bearing cationic or anionic substituents were examined for the efficiency of killing cancer cells (e.g., HeLa and CT26 carcinoma cells). The effectiveness of cell killing was observed in the following order: Pd(II) > cationic In(III) > cationic Zn(II) > anionic Zn(II) imidazolium-porphyrin. Hydroxymethyl-porphyrins and hydroxymethyl-chlorins were synthesized for studies of self-assembly in analogy with the structure and function of the natural pigment bacteriochlorophyll c. Various acyclic precursors containing a hydroxymethyl moiety (e.g., Mukaiyama reagents, 1-acyldipyrromethane) were prepared so that the hydroxymethyl group could be incorporated prior to the formation of the tetrapyrrole macrocycle. Formyl-chlorins were prepared for studies of the effect of the formyl group on the absorption spectral properties. Both hydroxymethyl-chlorins and formyl-chlorins were synthesized by the palladium-mediated coupling of the corresponding bromo-chlorin. Two routes were employed: (1) synthesis of a hydroxymethyl-chlorin via Stille coupling, followed by PCC-mediated oxidation to access the formyl-chlorin, and (2) palladium-catalyzed reductive carbonylation of a bromo-chlorin to access the formyl-chlorin. The ability to incorporate imidazole (and imidazolium), hydroxymethyl, and formyl groups at designated sites in porphyrins and chlorins affords valuable methodology for constructing molecular architectures of use in a variety of biological and materials chemistry applications.
The Use of Biodegradable Poly(b-amino ester) and Poly(b-amino amide) Microspheres as an Experimental Therapeutic Delivery Vector for Selective Cancer Cell Targeting
(2005-02-25) Shipton, Matthew Kent; Dr. Daniel Feldheim, Committee Chair; David A. Shultz, Committee Member; Edmond F. Bowden, Committee Member
The design, synthesis, and use of new biodegradable polymers for drug delivery applications is an area of ever increasing interest. Polymeric drug delivery systems have several advantages compared to conventional drug delivery methods such as liposomes and antibodies. Since liposomes are spherical vessels made of phosphorolipids, they are tiny particles which can be taken up by the macrophages. Antibodies, meanwhile, have the disadvantage that most receptor sites on tumor cells are also present on healthy cells. Several of these advantages include localized delivery, improved drug efficiency, and drug protection of certain medications which may degrade rapidly when inside the body. Poly(b-amino esters) and Poly(b-amino amides) are ideal polymers for the encapsulation, delivery, and release of various therapeutic agents to cancer cells, which have an acidic extra cellular pH level, near 6.8. Poly(b-amino esters) and Poly(b-amino amides) are specifically designed to degrade by hydrolysis of the ester and amide bonds respectively, in the polymer backbone. Microspheres of Poly(b-amino ester) and Poly(b-amino amide) are formed via a double emulsion process using Rhodamine B-Isothiocyanate (RBITC) labeled Bovine Serum Albumin (BSA) as the encapsulate. The fluorescence intensity of the RBITC-BSA released from the polymer sphere was measured as a way of testing polymer backbone hydrolysis. The polymer microspheres were placed into different solutions of varying pH ranges. The pH range extended from pH 5.5 to pH 7.4. The hydrolyzed polymer byproducts were removed and the resulting supernatant tested for fluorescence intensity. The results showed polymer hydrolysis and release of labeled BSA at pH 6.8 and lower.