Coumarin and cinnamate derivatives were positioned as either polymer chain ends or side groups to synthesize photoactive macromolecules and gain the ability to reversibly control molecular weight and crosslink density using UV light. The cinnamates and coumarins were reacted onto the polymers via multiple reaction pathways. Polymers were functionalized with coumarin or cinnamate groups via an esterification reaction between hydroxyl functionalities and an acid chloride derivatized coumarin group. In addition to the esterification reaction, cinnamates were also coupled to polymers via a ring opening reaction between a hydroxyl functionalized cinnamate derivative and a maleic anhydride repeat unit copolymerized into the polymer. Both functional groups undergo a [2π + 2π] photodimerization reaction (coumarin groups in the UVA and cinnamate groups in the UVB), which was utilized to crosslink and chain-extend macromolecules. Coumarin dimers possess the additional ability to photocleave and thus reverse when irradiated at 254 nm. The coumarin reversible photodimerization reaction was utilized to reversibly increase the molecular weight and molecular weight distribution of coumarin-functionalized PEG monols and diols. For example, the number average molecular weight of the coumarin-functionalized PEG diol doubled and the molecular weight distribution increased from 1.08 to 2.75 when exposed to 110 J cm⁻² of UVA irradiation. Subsequent photocleavage (UVC irradiation, 2 J cm⁻²) of the chain-extended PEGs, cleaved coumarin dimers decreasing the molecular weight and molecular weight distribution to their original values. A number of poly(alkyl acrylate) and poly(methyl acrylate) systems were functionalized with coumarin groups to study the effect of the glass transition temperature and alkyl ester side group composition on the photodimerization reaction and subsequent crosslinking. The glass transition temperature (T_g) acted as an on/off switch for the photodimerization reaction. While the absolute difference between T_g and irradiance temperature did not affect the rate or extent of photodimerization reaction, polymers with a T_g greater than the irradiance temperature displayed less reaction than those with a T_g lower than the irradiance temperature. The final extent of conversion was controlled by a complex combination of factors including alkyl ester side chain steric bulkiness. Coumarin-functionalized alkyl acrylates based on ethylhexyl acrylate were tested as detachable PSAs. A 98% decrease in the adhesive peel strength was observed after exposure to UVA irradiation. Cinnamate groups were utilized in the design and synthesis of UV-curable hot melt pressure sensitive adhesives (PSAs). The cinnamate groups were attached to the PSAs to provide a method to increase molecular weight and add a small amount of crosslinking leading to an increase the adhesive strength of the PSAs. Broadband UV irradiation from a laboratory scale industrial lamp increased the peel strength of the adhesives. Postcure of the irradiated cinnamate-functionalized UV-curable hot melt PSAs was reduced compared to photoinitiated free-radical photocurable UV-curable hot melt PSAs. / Ph. D.

The stable free radical polymerization methodology for production of controlled macromolecules was investigated using a novel monomer, 2-vinylnaphthalene. Initial polymerizations resulted in molecular weight distributions typical of conventional free radical polymerization techniques (>2.0). Manipulation of the initiator concentration and the molar ratio of initiator to nitroxide demonstrated no significant control over the resulting polymer products. Analysis of the polymerization kinetics for a 2-vinylnaphthalene polymerization performed in the presence and absence of the free radical initiator revealed identical monomer consumption profiles as well as pseudo first order kinetics indicating a significant degree of the thermal polymerization was occurring at the polymerization temperature (130°C). Comparison of the thermal polymerization propensity of 2-vinylnaphthalene and styrene revealed an increased tendency for 2-vinylnapthahlene to undergo thermal polymerization. Styrene is considered highly active in its propensity to thermally polymerize. However, an Arhenius analysis using in situ FTIR was employed to determine the activation energy for the thermal polymerization of styrene and 2-vinylnaphthalene. The 2-vinylnaphthalene activation energy for thermal polymerization was determined for the first time to be almost 30 kJ/mol less than styrene. A novel modified Mayo mechanism was proposed for the 2-vinylnaphthalene thermal initiation mechanism. Moreover, this thermal initiation was employed to initiate nitroxide mediated polymerizations of styrene. This first use of a 2-vinylnaphthalene initiating system resulted in polystyrene with a large macrocyclic initiating fragment. The presence of the initiating moiety was studied using both UV-Vis spectroscopy and 1H NMR spectroscopy. The extension of stable free radical polymerization to the acrylate monomer family was examined using a novel nitroxide mediator, N-tert-butyl-N-[1-diethylphosphono-(2,2-dimethylpropyl)] nitroxide (DEPN). The synthesis of DEPN was monitored using in situ FTIR spectroscopy to determine optimum reaction conditions. The purified nitroxide was subsequently employed in the synthesis of various block and random acrylate copolymers. The production of a unique amphiphilic block copolymer consisting of acrylic sequences was achieved. Poly(t-butyl acrylate-b-2ethylhexyl acrylate-b-t-butyl acrylate) was synthesized using the SFRP process. The t-butyl functionalities were subsequently removed in a post-polymerization acid catalyzed hydrolysis. The effect of steric bulk and electronic factors on the resulting SFRP process was also investigated and revealed similar polymerization kinetics for various alkyl acrylates. However, addition of a hydroxyl containing monomer, 2-hydroxyethyl acrylate, resulted in an increase in the polymerization rate up to 2 times. The rate enhancement was attributed to hydrogen bonding effects and this was confirmed using the unprecedented addition of dodecanol, which also demonstrated a significant rate enhancement. Block copolymers were also achieved using a novel difunctional nitroxide synthesized from 4-hydroxy TEMPO and 1,6-hexamethylene diisocyanate. The identity of the nitroxide was confirmed using mass spectrometry and 1H NMR. The dinitroxide was used in the polymerization of styrene and subsequently used to produce symmetric ABA triblock copolymers with t-butyl styrene using a unique two-step polymerization route. In addition, the dinitroxide demonstrated an increased tendency for decomposition due to the complex mediation equilibrium. The decomposition was studied using GPC to evaluate the decomposition effects on the polymerization. Results of the research efforts presented herein are written as individual research reports with contributing authors and pertinent literature reviews presented at the beginning of each chapter. / Ph. D.